Front driveshaft turning?
lelske
07-08-2008, 10:55 AM
So I was in Canada last week doing some fishing. With my trusty 1999 silverado 5.3-Autotrack 4wd.
On one of the runs back to the cabin, one of my rear rubber spacer bushings fell off (the ones that are installed between the axle and frame to prevent bottoming out).-It was the passenger side rear bushing that fell out.
Instead of trying to reattach it, I foolishly loaded up the truck and headed for home at the end of the week.
Shortly after taking off, I could hear the truck bed bottoming out against the axle...it wasn't a horribly loud sound, just the sound of metal on metal when we went over some decent bumps...
Immediately after one of the bottoming out sounds, there was a grinding noise that has stayed on since that time. It is noticeable starting at about 15mph, all the way to 60-65 when the road sound is too much to tell, but I assume it is there.
It sounds like the truck would normally sound if I activated the Auto 4WD button on the dash (like the front driveshaft is turning?), but the truck is in 2HI. When I now switch into Auto 4WD, there is no additional sounds that I can tell. I cannot verify what it did sound like, but if I remember correctly, I thought I could tell just by the sound when it was in 2Hi and then Auto 4WD made an additional sound. Am I remembering correctly?
It does not act like the truck is in 4Hi. I can enter that mode and tell the front tires are pulling, then re-enter 2hi and it sounds like Auto.
So my question is:
Should the front driveshaft turn in 2Hi? Or is that something that is only supposed to happen in Auto?
After two hours, I stopped and reattached the rubber bushing with duct tape and the bottoming out stopped (go figure), but I am afraid the damage may have already been done. I did drive it home for 15 hours after that, sound always stayed there and the truck never seemed to give me any other problems.
Any suggestions on what to check?
Thanks for your time and help!
On one of the runs back to the cabin, one of my rear rubber spacer bushings fell off (the ones that are installed between the axle and frame to prevent bottoming out).-It was the passenger side rear bushing that fell out.
Instead of trying to reattach it, I foolishly loaded up the truck and headed for home at the end of the week.
Shortly after taking off, I could hear the truck bed bottoming out against the axle...it wasn't a horribly loud sound, just the sound of metal on metal when we went over some decent bumps...
Immediately after one of the bottoming out sounds, there was a grinding noise that has stayed on since that time. It is noticeable starting at about 15mph, all the way to 60-65 when the road sound is too much to tell, but I assume it is there.
It sounds like the truck would normally sound if I activated the Auto 4WD button on the dash (like the front driveshaft is turning?), but the truck is in 2HI. When I now switch into Auto 4WD, there is no additional sounds that I can tell. I cannot verify what it did sound like, but if I remember correctly, I thought I could tell just by the sound when it was in 2Hi and then Auto 4WD made an additional sound. Am I remembering correctly?
It does not act like the truck is in 4Hi. I can enter that mode and tell the front tires are pulling, then re-enter 2hi and it sounds like Auto.
So my question is:
Should the front driveshaft turn in 2Hi? Or is that something that is only supposed to happen in Auto?
After two hours, I stopped and reattached the rubber bushing with duct tape and the bottoming out stopped (go figure), but I am afraid the damage may have already been done. I did drive it home for 15 hours after that, sound always stayed there and the truck never seemed to give me any other problems.
Any suggestions on what to check?
Thanks for your time and help!
ukrkoz
07-08-2008, 08:12 PM
there's a good rule of thumb:
don't fix it if it ain't brok. if it's brok, fix it RIGHT AWAY
(canadians have 3rd line to it - use ductape to fix everything. Red Green)
anyways, answer is - YES.
think about it. halfshaft is BOLTED into the hub and hub SPINS along with the wheel. of course halfshaft turns as wheel turns.
they free-spin as long as you are in 2wd mode.
they are engaged but no torque is supplied to them in 4auto mode.
they have torque supplied to them continuosly in 4wd hi and 4wd lo modes.
sounds like you bent something back there, when that truckbed landed on the axle.:crying: :crying:
don't fix it if it ain't brok. if it's brok, fix it RIGHT AWAY
(canadians have 3rd line to it - use ductape to fix everything. Red Green)
anyways, answer is - YES.
think about it. halfshaft is BOLTED into the hub and hub SPINS along with the wheel. of course halfshaft turns as wheel turns.
they free-spin as long as you are in 2wd mode.
they are engaged but no torque is supplied to them in 4auto mode.
they have torque supplied to them continuosly in 4wd hi and 4wd lo modes.
sounds like you bent something back there, when that truckbed landed on the axle.:crying: :crying:
lelske
07-08-2008, 10:23 PM
Thanks for your reply. I have a couple of questions...
First, what is the halfshaft? Is that the forward drive shaft?
Second, what could I have bent in the rear that caused the forward driveshaft to stay engaged?
When I press the Auto/2Hi buttons, I can hear the front solenoid actuate as if it was trying to do something, but it doesn't free up the driveshaft.
Again, thanks for all of your help.
First, what is the halfshaft? Is that the forward drive shaft?
Second, what could I have bent in the rear that caused the forward driveshaft to stay engaged?
When I press the Auto/2Hi buttons, I can hear the front solenoid actuate as if it was trying to do something, but it doesn't free up the driveshaft.
Again, thanks for all of your help.
ukrkoz
07-08-2008, 11:17 PM
Thanks for your reply. I have a couple of questions...
First, what is the halfshaft? Is that the forward drive shaft?
Second, what could I have bent in the rear that caused the forward driveshaft to stay engaged?
When I press the Auto/2Hi buttons, I can hear the front solenoid actuate as if it was trying to do something, but it doesn't free up the driveshaft.
Again, thanks for all of your help.
our trucks have 3 shafts: 1 driveshaft that goes from transfer case to the rear differential and 2 shafts that go from the front differential to the front wheels. those are called halfshafts, as they are much shorter than the main driveshaft.
sorry, i was not explicit enough. halfshafts, as they are permanently attached to the center of the hub via splines/center shaft nut, spin every time wheel spins. it has nothing to do with transmission/transfer case/differential. it is simple mechanical connection because, when torque is applied to the halfshaft, it has to turn the wheel, so when no torque is applied to it (2HI mode) it simply is turned by the rolling wheel. i think, you were not sure if it is supposed to turn all the time. yes.
in auto 4wd, halfshaft is engaged by transfer case, but no torque(power) is applied to it. it is applied only when sensors sense rear wheel slipping, then transfer case redirects torque(power) to all 4 wheels. because it is engaged, you feel slight drop in general power and slight noise added at higher speeds.
when the 4Hi mode is activated, halfshafts are not only engaged, but torque(power) is more or less equelly distributued, all the time, to all 4 wheels, turning teuck into 4 WD machine. this results in more pronounced drop in general power, slow down, slower pickup, and higher level of noise due to many gears spinning, etc. speed is not recommended to cross 50mph.
hope, this answered your question.
i am assuming, that while you were offroading, you hit pothole with loaded truck, and truckbed went all the way down and hit the axle. well, i'd start with general visual inspection of driveaxle/rear diff/rear tirewell. 2ndly, it is easy to assume that impact could have damaged rear diff or one of the hub bearings in the rear hubs. any of those could result in noises coming from the REAR end.
transfer case in silvies is positioned more or less down the midline of the truck sidewise. any time truckbed moves up and down, rear axle moves back and forth in relationship to the transfer case, thus they have slip yoke in the drive shaft, that slides back and forth in the transfer case, to accomodate for such displacements. EXTREME movements of the truck bed could cause driveshaft impacting the transfer case. once again, i'd inspect visually. simply put, you need to get your truck up in the air safely and inspect the whole undercarriage.
also, get a buddy, then go to some slippery area. large mud pit will do fine. get your truck into it, while your buddy stands outside and observes your wheels. engage 2HI. then step on the gas pedal. if only rear wheels slip in the mud - you good. if both front and rear wheels slip in the mud - you got yourslef a problem with transfer case stuck in auto 4wd. you would know 4HI, as it manifests itself all too well.
PS i used "movement of truckbed" only as relevant to your situation. it is the wheels that move up and down, thus changing the distance from the rear diff to the transfer case, but for your point of reference - let's say it's truckbed moving, ok?
First, what is the halfshaft? Is that the forward drive shaft?
Second, what could I have bent in the rear that caused the forward driveshaft to stay engaged?
When I press the Auto/2Hi buttons, I can hear the front solenoid actuate as if it was trying to do something, but it doesn't free up the driveshaft.
Again, thanks for all of your help.
our trucks have 3 shafts: 1 driveshaft that goes from transfer case to the rear differential and 2 shafts that go from the front differential to the front wheels. those are called halfshafts, as they are much shorter than the main driveshaft.
sorry, i was not explicit enough. halfshafts, as they are permanently attached to the center of the hub via splines/center shaft nut, spin every time wheel spins. it has nothing to do with transmission/transfer case/differential. it is simple mechanical connection because, when torque is applied to the halfshaft, it has to turn the wheel, so when no torque is applied to it (2HI mode) it simply is turned by the rolling wheel. i think, you were not sure if it is supposed to turn all the time. yes.
in auto 4wd, halfshaft is engaged by transfer case, but no torque(power) is applied to it. it is applied only when sensors sense rear wheel slipping, then transfer case redirects torque(power) to all 4 wheels. because it is engaged, you feel slight drop in general power and slight noise added at higher speeds.
when the 4Hi mode is activated, halfshafts are not only engaged, but torque(power) is more or less equelly distributued, all the time, to all 4 wheels, turning teuck into 4 WD machine. this results in more pronounced drop in general power, slow down, slower pickup, and higher level of noise due to many gears spinning, etc. speed is not recommended to cross 50mph.
hope, this answered your question.
i am assuming, that while you were offroading, you hit pothole with loaded truck, and truckbed went all the way down and hit the axle. well, i'd start with general visual inspection of driveaxle/rear diff/rear tirewell. 2ndly, it is easy to assume that impact could have damaged rear diff or one of the hub bearings in the rear hubs. any of those could result in noises coming from the REAR end.
transfer case in silvies is positioned more or less down the midline of the truck sidewise. any time truckbed moves up and down, rear axle moves back and forth in relationship to the transfer case, thus they have slip yoke in the drive shaft, that slides back and forth in the transfer case, to accomodate for such displacements. EXTREME movements of the truck bed could cause driveshaft impacting the transfer case. once again, i'd inspect visually. simply put, you need to get your truck up in the air safely and inspect the whole undercarriage.
also, get a buddy, then go to some slippery area. large mud pit will do fine. get your truck into it, while your buddy stands outside and observes your wheels. engage 2HI. then step on the gas pedal. if only rear wheels slip in the mud - you good. if both front and rear wheels slip in the mud - you got yourslef a problem with transfer case stuck in auto 4wd. you would know 4HI, as it manifests itself all too well.
PS i used "movement of truckbed" only as relevant to your situation. it is the wheels that move up and down, thus changing the distance from the rear diff to the transfer case, but for your point of reference - let's say it's truckbed moving, ok?
lelske
07-09-2008, 07:35 AM
Again, thanks for your help. I am sorry to be a pain, but I still have a couple of questions.
The front drive shaft I was thinking of was the shaft that connects the differential in the center of the truck (same differential that is connected to the rear, main driveshaft) to the front transaxle, not the shafts that connect the front differential to each of the front wheels.
As far as I can tell, my truck only has one of those...then it goes to the front differential, then 2 shafts to the wheels....
Not that I didn't bottom out the truck, everything you say may very well be possible, I did a quick inspection and found nothing obviously broken, bent or leaking, and when spinning the rear wheels, it didn't sound or feel like a bearing.
And I am 99% sure that my truck is not in 4wd ( I hope I didn't drive it home 15 hours at 65mph in 4hi....that should cause considerably less than the 14mpg I got on the way home). I can press the 4hi button and feel the difference in power going to the front wheels, as well as the sounds and feel of the front wheels when turning on pavement...it is a very significant change once I press the 4hi button and then again back to 2hi.
But my theory is that with the auto trac 4wd system:
If the truck is in 2hi, the rear driveshaft spins, applying torque to the rear dif, making the truck move. Obviously the front halfshafts (attached directly to the front hubs) spin when the front wheels spin, but they are not being "driven" as the rear wheels are. As far as I can tell, the forward driveshaft (the shaft between center differential and front transaxle) should spin freely in 2hi mode.
If the truck is in Auto 4WD, the truck engages [what I call] the front drive shaft (the shaft between center differential and front transaxle) and then lets the slippage sensors determine when the rear wheels slip, and then the power is applied within the front differential to the front 2 halfshafts, causing the front wheels to "drive".
I checked my Dad's truck last night (1999 Suburban with autotrac) and his front driveshaft is not engaged while in 2hi (mine is). So I think it still might be something related to that.
Thanks again for all of your help.
The front drive shaft I was thinking of was the shaft that connects the differential in the center of the truck (same differential that is connected to the rear, main driveshaft) to the front transaxle, not the shafts that connect the front differential to each of the front wheels.
As far as I can tell, my truck only has one of those...then it goes to the front differential, then 2 shafts to the wheels....
Not that I didn't bottom out the truck, everything you say may very well be possible, I did a quick inspection and found nothing obviously broken, bent or leaking, and when spinning the rear wheels, it didn't sound or feel like a bearing.
And I am 99% sure that my truck is not in 4wd ( I hope I didn't drive it home 15 hours at 65mph in 4hi....that should cause considerably less than the 14mpg I got on the way home). I can press the 4hi button and feel the difference in power going to the front wheels, as well as the sounds and feel of the front wheels when turning on pavement...it is a very significant change once I press the 4hi button and then again back to 2hi.
But my theory is that with the auto trac 4wd system:
If the truck is in 2hi, the rear driveshaft spins, applying torque to the rear dif, making the truck move. Obviously the front halfshafts (attached directly to the front hubs) spin when the front wheels spin, but they are not being "driven" as the rear wheels are. As far as I can tell, the forward driveshaft (the shaft between center differential and front transaxle) should spin freely in 2hi mode.
If the truck is in Auto 4WD, the truck engages [what I call] the front drive shaft (the shaft between center differential and front transaxle) and then lets the slippage sensors determine when the rear wheels slip, and then the power is applied within the front differential to the front 2 halfshafts, causing the front wheels to "drive".
I checked my Dad's truck last night (1999 Suburban with autotrac) and his front driveshaft is not engaged while in 2hi (mine is). So I think it still might be something related to that.
Thanks again for all of your help.
ukrkoz
07-09-2008, 10:08 AM
1. i see. so, you were referring to the main driveshaft, one that runs from the transfer case to the rear differential.
the configuration is as follows: engine/transmission/transfer case/main driveshaft/rear differential for the 2HI mode only. in addition, on 4WD models, transfer case has front differential attached, with 2 halfshafts coming out of it and connected to the wheel hubs bilateral.
2. with due respect to your dad's truck, it is physically impossible for the front halfshafts to not rotate, if the front wheels rotate, in 2Hi mode, as they are "permanently" attached to the wheel hubs and rotate every time a wheel(hub) is rotated. they are not engaged to the transfer case, with no power supplied to them, in 2HI mode. they are engaged but no power supplied in AUTO4WD, engaged and power supplied in 4HI.
but i feel this is not what you are fishing for and we might be talking about the same thing just in different words. i assume you feel like your truck is stuck in AUTO4WD whilst the transfer case switch is in 2HI position, that resulting in a specific noise coming from somewhere.
have you done the mud test? this is about the only way to find out, without bringing it to repair shop. which they will, most likely, do same test.
you might have 2 different situations, just coinsiding: bottoming of the truck bed and transfer case switch going bad. chevy transfer case switches, the push button ones, are notorious for going bad fast. i had mine replaced at 60K miles. but, normally, it'll throw service transmission/transfer case light on.
i, personally, wouldn't be content and rush to conclusions based on just superficial inspection. you may have foreign objects stuck anywhere in the rear hub assembly, bent splash shield/s, loose wire or cable, etc. there are many parts on those trucks that are in wrong places and just asking for being damaged, esp during offroading. though claimed to be so, it is NOT an offroading vehicle.
i still recommend the mud test, and if the front wheels have no power to them during it, with the switch in 2HI, then it's not the transfer case or switch, they work fine, and it's something else. next step would have been to find out where exactly is the noise coming from. front, rear, or mid car? hey, easy way is to get that truck on a lift, raise it up, get it into 2Hi, and put it into drive with engine on. if the front wheels do spin and you can't stop them with light hand resistance - you have a problem. also, you can run switch through different positions and see actuator working, with resulting different front wheels behaviour.
good luck. and no, you never were pain in anything, and i'll be more than content if i could help some.
the configuration is as follows: engine/transmission/transfer case/main driveshaft/rear differential for the 2HI mode only. in addition, on 4WD models, transfer case has front differential attached, with 2 halfshafts coming out of it and connected to the wheel hubs bilateral.
2. with due respect to your dad's truck, it is physically impossible for the front halfshafts to not rotate, if the front wheels rotate, in 2Hi mode, as they are "permanently" attached to the wheel hubs and rotate every time a wheel(hub) is rotated. they are not engaged to the transfer case, with no power supplied to them, in 2HI mode. they are engaged but no power supplied in AUTO4WD, engaged and power supplied in 4HI.
but i feel this is not what you are fishing for and we might be talking about the same thing just in different words. i assume you feel like your truck is stuck in AUTO4WD whilst the transfer case switch is in 2HI position, that resulting in a specific noise coming from somewhere.
have you done the mud test? this is about the only way to find out, without bringing it to repair shop. which they will, most likely, do same test.
you might have 2 different situations, just coinsiding: bottoming of the truck bed and transfer case switch going bad. chevy transfer case switches, the push button ones, are notorious for going bad fast. i had mine replaced at 60K miles. but, normally, it'll throw service transmission/transfer case light on.
i, personally, wouldn't be content and rush to conclusions based on just superficial inspection. you may have foreign objects stuck anywhere in the rear hub assembly, bent splash shield/s, loose wire or cable, etc. there are many parts on those trucks that are in wrong places and just asking for being damaged, esp during offroading. though claimed to be so, it is NOT an offroading vehicle.
i still recommend the mud test, and if the front wheels have no power to them during it, with the switch in 2HI, then it's not the transfer case or switch, they work fine, and it's something else. next step would have been to find out where exactly is the noise coming from. front, rear, or mid car? hey, easy way is to get that truck on a lift, raise it up, get it into 2Hi, and put it into drive with engine on. if the front wheels do spin and you can't stop them with light hand resistance - you have a problem. also, you can run switch through different positions and see actuator working, with resulting different front wheels behaviour.
good luck. and no, you never were pain in anything, and i'll be more than content if i could help some.
lelske
07-09-2008, 10:30 AM
"one that runs from the transfer case to the rear differential."
No, one that runs from the transfer case in the middle of the truck to the front differential...it looks just like the main driveshaft that goes to the rear axle, but it is about half as long, and goes to the front diff.
"on 4WD models, transfer case has front differential attached"
Yes, mine is a 4x4- the shaft I am referring to is what connects them together.
http://i267.photobucket.com/albums/ii303/fattyslimslim/0210or_shootout13_zoom.jpg
Does that clear it up? Should the shaft identified with the red arrow be turning 100% of the time no matter what mode is selected?
"i assume you feel like your truck is stuck in AUTO4WD whilst the transfer case switch is in 2HI position"
That is correct. Would there be any physical/noise difference between running in 2Hi and Auto4WD?
No, one that runs from the transfer case in the middle of the truck to the front differential...it looks just like the main driveshaft that goes to the rear axle, but it is about half as long, and goes to the front diff.
"on 4WD models, transfer case has front differential attached"
Yes, mine is a 4x4- the shaft I am referring to is what connects them together.
http://i267.photobucket.com/albums/ii303/fattyslimslim/0210or_shootout13_zoom.jpg
Does that clear it up? Should the shaft identified with the red arrow be turning 100% of the time no matter what mode is selected?
"i assume you feel like your truck is stuck in AUTO4WD whilst the transfer case switch is in 2HI position"
That is correct. Would there be any physical/noise difference between running in 2Hi and Auto4WD?
bigbadram51
07-09-2008, 12:00 PM
If this has been answered already, I apologize... Didnt feel like reading the answer that was almost a novel. With your Auto-Trac it should spin (front d-shaft) all the time. Newer Auto-tracs 04 and up dont spin in 4wd. If you are unsure, best way to test is to turn truck off, put in park, climb under truck and try to manually spin (front d-shaft) it. If it spins freely you have the newer version.
ukrkoz
07-09-2008, 12:16 PM
gotcha.
no, it should not be rotating in 2HI mode, front is completely disengaged from the transfer case.
matter of fact, just to make sure, i have just called chevy and they did confirm that that intermediate shaft should not be rotating.
so, you either have switch mulfunction, or transfer case mulfunction.
yes, there's faint noise driving with AUTO4WD engaged and slight drop in performance.
try putting your transfer case into transfer case neutral, like as if for towing. maybe it'll fix itself.
no, it should not be rotating in 2HI mode, front is completely disengaged from the transfer case.
matter of fact, just to make sure, i have just called chevy and they did confirm that that intermediate shaft should not be rotating.
so, you either have switch mulfunction, or transfer case mulfunction.
yes, there's faint noise driving with AUTO4WD engaged and slight drop in performance.
try putting your transfer case into transfer case neutral, like as if for towing. maybe it'll fix itself.
lelske
07-09-2008, 12:22 PM
gotcha.
no, it should not be rotating in 2HI mode, front is completely disengaged from the transfer case.
Intermediate shaft! Very clever name. I shall make a point to call it that from now on!
Very good, that is what I thought, and the faint noise and performance drop is exactly what I think I am seeing.
I will try TC neutral when I get home.
Thanks!
no, it should not be rotating in 2HI mode, front is completely disengaged from the transfer case.
Intermediate shaft! Very clever name. I shall make a point to call it that from now on!
Very good, that is what I thought, and the faint noise and performance drop is exactly what I think I am seeing.
I will try TC neutral when I get home.
Thanks!
ukrkoz
07-09-2008, 12:29 PM
what year is your truck? it appears we have identical or almost, mine is 2000 LT model, Z71 4WD, with auto transfer case, push button switch on the dashboard.
read your truck manual before neutralling it, it's a lengthy and tricky procedure.
all the best.
read your truck manual before neutralling it, it's a lengthy and tricky procedure.
all the best.
lelske
07-09-2008, 01:27 PM
what year is your truck? it appears we have identical or almost, mine is 2000 LT model, Z71 4WD, with auto transfer case, push button switch on the dashboard.
read your truck manual before neutralling it, it's a lengthy and tricky procedure.
all the best.
1999 LS Z71 4WD Ext cab, long box.
read your truck manual before neutralling it, it's a lengthy and tricky procedure.
all the best.
1999 LS Z71 4WD Ext cab, long box.
ukrkoz
07-09-2008, 01:45 PM
1999 LS Z71 4WD Ext cab, long box.
same truck, everything's same, only mine is LT 2000 model and Centurion edition. assembled in Canada.
i have repair manual for it at home, so if you need copies of pages or something, feel free.
keeping my fingers crossed on that TC neutralling. you might have smacked it so that it got stuck in AUTO4WD.
same truck, everything's same, only mine is LT 2000 model and Centurion edition. assembled in Canada.
i have repair manual for it at home, so if you need copies of pages or something, feel free.
keeping my fingers crossed on that TC neutralling. you might have smacked it so that it got stuck in AUTO4WD.
lelske
07-09-2008, 02:06 PM
very cool. I just ordered my manual...160K and now I need a manual....
I will come back with an update tonight.
Thanks for all the help.
I will come back with an update tonight.
Thanks for all the help.
lelske
07-09-2008, 06:53 PM
Well, I tried putting the TC in Neutral and let it roll for a bit. Same problem existed when I put it back in gear.
I also tried another 4WD switch that I had just replaced and went through the modes, same problem.
I will have to wait for the manual to show up to give me a clue on how the shaft engages/disengages with the TC.
I also tried another 4WD switch that I had just replaced and went through the modes, same problem.
I will have to wait for the manual to show up to give me a clue on how the shaft engages/disengages with the TC.
2000CAYukon
07-09-2008, 08:12 PM
How long has it been since the Auto-Trak fluid was replaced in the Transfer Case?
//2000CAYukon
//2000CAYukon
lelske
07-09-2008, 08:28 PM
How long has it been since the Auto-Trak fluid was replaced in the Transfer Case?
//2000CAYukon
My best guess? Probably since 1999. I know I haven't done it before but I am not sure if it was done in any previous servicing....
Is that a task I could do myself?
//2000CAYukon
My best guess? Probably since 1999. I know I haven't done it before but I am not sure if it was done in any previous servicing....
Is that a task I could do myself?
2000CAYukon
07-09-2008, 09:37 PM
My best guess? Probably since 1999. I know I haven't done it before but I am not sure if it was done in any previous servicing....
Is that a task I could do myself?
That is a long time. This is a drain and fill operation. I got my Auto-Trak fluid from an AC Delco Parts store but I guess you can also get it from a dealer. I bought 3 qts but it ended up only using 2 qts.
I used one of those pumps that you can buy at an Auto Parts store and pumped it right out of the Auto Trak bottle.
//2000CAYukon
Is that a task I could do myself?
That is a long time. This is a drain and fill operation. I got my Auto-Trak fluid from an AC Delco Parts store but I guess you can also get it from a dealer. I bought 3 qts but it ended up only using 2 qts.
I used one of those pumps that you can buy at an Auto Parts store and pumped it right out of the Auto Trak bottle.
//2000CAYukon
ukrkoz
07-10-2008, 11:30 AM
matter of fact, rear diff, front diff, transfer case fluids are recommended to be replaced at 60K miles. it's no big deal to DIY, but buy OEM fluids, gmc has weird ones. ac/delco will work, as ac/delco and gmc are in total kahutz.
i purchased a $16 worth handpump for oils and fluids from schucks, was very good investment. invalueable for this type of jobs. MUCH faster and convenient. just don't forget to flush it if you oscillate between different types of fluids.:nono: :nono:
i purchased a $16 worth handpump for oils and fluids from schucks, was very good investment. invalueable for this type of jobs. MUCH faster and convenient. just don't forget to flush it if you oscillate between different types of fluids.:nono: :nono:
lelske
08-07-2008, 11:32 AM
Just an update...I got my repair manual so I have tried a few more things...
I removed the electric shift motor from the transfer case and pressed the button on the dash, shifting it from 2hi to auto to 4hi, etc...the motor seemed to respond properly. It only moved the actuator about 1/8 of a turn each time it was pressed. I was also able to hear the motor turn when back on the transfer case so if my thinking is right the TC control switch and the TC contol module, as well as the TC shift motor should all be functioning, agreed?
So I changed the TC fluid, and the problem still exists. The dealer suggested it was clutches within the TC and recommended the entire TC be replaced.
So far anybody have any differing opinions?
I bought a used TC from a junkyard ($350) and am planning on putting it in this weekend.
Anyone have any helpful hints or warnings about such a project?
Thanks again to everyone for all of your help.
I removed the electric shift motor from the transfer case and pressed the button on the dash, shifting it from 2hi to auto to 4hi, etc...the motor seemed to respond properly. It only moved the actuator about 1/8 of a turn each time it was pressed. I was also able to hear the motor turn when back on the transfer case so if my thinking is right the TC control switch and the TC contol module, as well as the TC shift motor should all be functioning, agreed?
So I changed the TC fluid, and the problem still exists. The dealer suggested it was clutches within the TC and recommended the entire TC be replaced.
So far anybody have any differing opinions?
I bought a used TC from a junkyard ($350) and am planning on putting it in this weekend.
Anyone have any helpful hints or warnings about such a project?
Thanks again to everyone for all of your help.
kahjdh
08-07-2008, 10:32 PM
Wait a sec, front drive shaft shouldnt spin, there is an actuator on the front axle that locks the right half-sshaft into the diff when the TC is shifted.
lelske
08-08-2008, 08:26 AM
Wait a sec, front drive shaft shouldnt spin, there is an actuator on the front axle that locks the right half-sshaft into the diff when the TC is shifted.
And there is also a electric shift motor on the transfer case that engages the intermediate shaft to start spinning in auto 4wd mode so the power is already to the front diff when the actuator you speak of needs to kick in, then you have power to the front wheels. That part of my truck seems to work fine- the problem is that my intermediate shaft never disconnects from the transfer case, thus it is always spinning regardless of what 4wd mode it is in (2hi)..it causes a little more noise, lower gas mileage, and I would imagine if I let it continue, it could burn up the front diff? especially towing at interstate speeds (75+)...
And there is also a electric shift motor on the transfer case that engages the intermediate shaft to start spinning in auto 4wd mode so the power is already to the front diff when the actuator you speak of needs to kick in, then you have power to the front wheels. That part of my truck seems to work fine- the problem is that my intermediate shaft never disconnects from the transfer case, thus it is always spinning regardless of what 4wd mode it is in (2hi)..it causes a little more noise, lower gas mileage, and I would imagine if I let it continue, it could burn up the front diff? especially towing at interstate speeds (75+)...
lelske
10-02-2008, 07:56 AM
Just a quick update to my problem...I replaced the transfer case (with one from a salvage yard) and the problem still existed. I dodn't have access to a transmission scan tool so I needed the tranny fluid flushed anyway so I took it to the best tranmission/transfer case shop in town.
They told me that all of their sources say that front (intermediate) driveshaft should be locked in all of the time but that my noise that I was experiencing was coming from the front differential.
He took it apart and found the bearings to be bad, they were replaced (at some $1200!!!!) and the truck now sounds normal again.
I did drive it home and switched to AUTO4 and I now hear what I think is normal, a smaller noise, much smaller noise than my truck was making before...I checked it when I got home, and that front shaft was locked in again, in 2HI, so I am not sure if that is normal yet or not...
I need to find a similar truck on a car lot and check it out...
They told me that all of their sources say that front (intermediate) driveshaft should be locked in all of the time but that my noise that I was experiencing was coming from the front differential.
He took it apart and found the bearings to be bad, they were replaced (at some $1200!!!!) and the truck now sounds normal again.
I did drive it home and switched to AUTO4 and I now hear what I think is normal, a smaller noise, much smaller noise than my truck was making before...I checked it when I got home, and that front shaft was locked in again, in 2HI, so I am not sure if that is normal yet or not...
I need to find a similar truck on a car lot and check it out...
lelske
10-02-2008, 08:14 AM
I forgot to add that the shop checked for TC codes and found none. I was hoping there was something in the system that was failing to disengage the front (intermediate) driveshaft.
ukrkoz
10-02-2008, 09:49 AM
I need to find a similar truck on a car lot and check it out...
1. as you remember, i called Best Chevrolet here in renton, and they told that intermediate shaft should not be turning and that's that a problem that needs to be looked at. of course, it's dealer's talk.
2. i'll have my truck on a lift this saturday. we are replacing tierods, terod ends, and pulling driveshaft out to check on yoke. i'll do my best to check that shaft to see if it locks or turns free on mine. matter of fact, if you want to pm me, i'll give you my ph number, call me saturday to remind me of this.
3. it does make a different sound in auto4wd, more - in 4hi.
btw:(from another post)
Hi Timothy,
There is no logical reason why it should do that, as you are aware.
The front axle shafts turn all the time, unless you have some kind of locking hubs.
If you do have locking hubs, I would say the right side is not locking.
There is an actuator that directly connects the right axle shaft to the front differential when 4X4 is engaged, but if it isn't working, it usually doesn't cause the truck to pull to one side...it usually causes the front to not pull at all.
Even the left side, which splines directly into the side gear of the front differential shouldn't have any extra pull or drag, due to the differential action inside.
Now, if you have some kind of limitid slip, or locking differential on the front axle, which extreme rock climbers have, then I could see the actuator not working, and having the effect you describe.
You could leave 4X4 engaged, and jack up the front axle, and see if you can rotate the front tires.With a stock front differential, the wheels should rotate in opposite directions, and do it rather easily, and the front driveshaft should not turn.
With 4X4 shifted to two wheel drive, you should be able to rotate the front driveshaft, but neither wheel rotate.
The actuator is removable without loosing any oil, and you can test it outside the axle housing.
Van
1. as you remember, i called Best Chevrolet here in renton, and they told that intermediate shaft should not be turning and that's that a problem that needs to be looked at. of course, it's dealer's talk.
2. i'll have my truck on a lift this saturday. we are replacing tierods, terod ends, and pulling driveshaft out to check on yoke. i'll do my best to check that shaft to see if it locks or turns free on mine. matter of fact, if you want to pm me, i'll give you my ph number, call me saturday to remind me of this.
3. it does make a different sound in auto4wd, more - in 4hi.
btw:(from another post)
Hi Timothy,
There is no logical reason why it should do that, as you are aware.
The front axle shafts turn all the time, unless you have some kind of locking hubs.
If you do have locking hubs, I would say the right side is not locking.
There is an actuator that directly connects the right axle shaft to the front differential when 4X4 is engaged, but if it isn't working, it usually doesn't cause the truck to pull to one side...it usually causes the front to not pull at all.
Even the left side, which splines directly into the side gear of the front differential shouldn't have any extra pull or drag, due to the differential action inside.
Now, if you have some kind of limitid slip, or locking differential on the front axle, which extreme rock climbers have, then I could see the actuator not working, and having the effect you describe.
You could leave 4X4 engaged, and jack up the front axle, and see if you can rotate the front tires.With a stock front differential, the wheels should rotate in opposite directions, and do it rather easily, and the front driveshaft should not turn.
With 4X4 shifted to two wheel drive, you should be able to rotate the front driveshaft, but neither wheel rotate.
The actuator is removable without loosing any oil, and you can test it outside the axle housing.
Van
lelske
10-02-2008, 10:22 AM
I would agree that it makes sense that it should turn freely, I just never checked mine before all of this happened.
I cannot figure out what else could be wrong/replaced. I was hoping the scan codes might tell me the TCCM might be having a problem but that didn't happen either.
I have not jacked it up recently and spun the front wheels/shaft to see what happens. I will try to do that.
I will be out of town this weekend hunting, and out of cell range, but if you happen to think about it, I would greatly appreciate it if you could just check how the shaft acts in 2hi?
I guess it is possible that the original TC was damaged during the bottom out, but this is the second salvage yard TC that acts this way as well.
I haven't taken apart my original TC to see how the clutches work with the actuator inside, but my personal belief is that the front driveshaft should disconnect at the TC but this is now three TCs that are not doing that...
and regarding the sound, my truck now does make a slightly different sound in auto4 than in 2hi and an even greater sound in 4hi, so that is acting like it should I believe.
I cannot figure out what else could be wrong/replaced. I was hoping the scan codes might tell me the TCCM might be having a problem but that didn't happen either.
I have not jacked it up recently and spun the front wheels/shaft to see what happens. I will try to do that.
I will be out of town this weekend hunting, and out of cell range, but if you happen to think about it, I would greatly appreciate it if you could just check how the shaft acts in 2hi?
I guess it is possible that the original TC was damaged during the bottom out, but this is the second salvage yard TC that acts this way as well.
I haven't taken apart my original TC to see how the clutches work with the actuator inside, but my personal belief is that the front driveshaft should disconnect at the TC but this is now three TCs that are not doing that...
and regarding the sound, my truck now does make a slightly different sound in auto4 than in 2hi and an even greater sound in 4hi, so that is acting like it should I believe.
lelske
10-02-2008, 10:38 AM
and I called another place in town, the local 4wd jeep service place, he says that there should be drag on the driveshaft, but not locked in like the rear feels like (mine is locked in).
So he guesses clutches within the transfer case, actuator switch, sensors, wiring, or bcm...
perhaps I will have the guts (read: money) to have him look at it sometime.
So he guesses clutches within the transfer case, actuator switch, sensors, wiring, or bcm...
perhaps I will have the guts (read: money) to have him look at it sometime.
ukrkoz
10-04-2008, 04:55 PM
[quote=lelske]and I called another place in town, the local 4wd jeep service place, he says that there should be drag on the driveshaft, but not locked in like the rear feels like (mine is locked in).
So he guesses clutches within the transfer case, actuator switch, sensors, wiring, or bcm...
quote]
ok, boss, i have the final answer for you.
with the truck on lift, engine turned off, and in either drive or neutral, intermediate drveshaft can be spun with hand, without spinning wheels.
there's some drag in, yes, but it is not enough to warrant what you describing.:nono: :nono: :nono:
see, i was a good person and did not forget to check. :wink:
So he guesses clutches within the transfer case, actuator switch, sensors, wiring, or bcm...
quote]
ok, boss, i have the final answer for you.
with the truck on lift, engine turned off, and in either drive or neutral, intermediate drveshaft can be spun with hand, without spinning wheels.
there's some drag in, yes, but it is not enough to warrant what you describing.:nono: :nono: :nono:
see, i was a good person and did not forget to check. :wink:
lelske
10-06-2008, 07:17 AM
ok, boss, i have the final answer for you.
with the truck on lift, engine turned off, and in either drive or neutral, intermediate drveshaft can be spun with hand, without spinning wheels.
there's some drag in, yes, but it is not enough to warrant what you describing.:nono: :nono: :nono:
see, i was a good person and did not forget to check. :wink:[/QUOTE]
Awesome. Thanks for the information. I will continue to look for a solution!
with the truck on lift, engine turned off, and in either drive or neutral, intermediate drveshaft can be spun with hand, without spinning wheels.
there's some drag in, yes, but it is not enough to warrant what you describing.:nono: :nono: :nono:
see, i was a good person and did not forget to check. :wink:[/QUOTE]
Awesome. Thanks for the information. I will continue to look for a solution!
trbolvr
02-21-2009, 04:44 PM
Here is what I found on my 99 1500 Silverado. I believe the front drive shaft is turning because of residual friction from the clutch plates/steels inside the np246 transfer case. I was pondering the same issue this past week while replacing front u joints. I had the TC in neutral and it felt like the front and rear shafts were locked together. I placed a prybar in the front u joint to hold it in place and was able to turn the rear shaft with a large channel locks. There was a substantial amount of force needed to turn the rear shaft independant of the front. Probably not the best for gas milage as the front pinion and ring gear are spinning away in 2 high. Here are couple good articles on the np246 (nv246 seems to be the same unit). http://www.rsgear.com/articles/2004_12.pdf http://www.rsgear.com/articles/2005_09.pdf .
lelske
02-24-2009, 12:03 PM
That is some fantastic information. I sure wish I had it before replacing my TC twice. But you live and learn I guess.
My truck is the same way-as far as turning the driveshafts....I had a TC specialist (from our areas best 4wd center) look at it and he is convinced that it is operating properly. I still have yet to determine the cause of the mileage decrease, but at least it is good to know that the TC is working like it should.
I love those links you sent me. I was looking for so many weeks for something like that.
I will be sure to print them out and add them to my collection of paperwork.
Thanks!
My truck is the same way-as far as turning the driveshafts....I had a TC specialist (from our areas best 4wd center) look at it and he is convinced that it is operating properly. I still have yet to determine the cause of the mileage decrease, but at least it is good to know that the TC is working like it should.
I love those links you sent me. I was looking for so many weeks for something like that.
I will be sure to print them out and add them to my collection of paperwork.
Thanks!
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