Oh Boy!!!!

Alright 98 Blazer

Out on lake doing some ice fishing up here in Minnesota(damn Cold).

Driving across the ice and hit a big drift, yeap she is stuck. So I am shifting back and forth from Drive and Reverse in 4x4 3 button push. Bout 10 shifts, and then I started getting the sound of two gears slipping, and the tires didnt appear to be spinning they just kind of jolted a little, so I would let off the gas and shift gears and sometimes it would catch and the wheels were normal again, but then after shifting that noise was back, best way to describe it was like a ratcheting noise. So I finally get out and all is good, noise is gone, 4x4 is working. Somthing must be wrong but, not sure what. I mean being stuck in the snow is not much load on the tires, I can sit on dry pavement and smoke them all day long and never have herd that ratcheting noise.

Check the cable from the actuator to the front diffy. Since it it basically hanging out ther in the breeze, it may have been bound or kinked after having settled into the drift, then retunred to normal once you got off the drift.

alright was playing in the snow today, 4x4 not working at all. The front drive shaft is engaged all time, in 2wd and 4wd, but front diff is not engageing. What would cause this. I plan on pulling it into the shop and looking at it this evening. Any tips would be helpful.

alright was playing in the snow today, 4x4 not working at all. The front drive shaft is engaged all time, in 2wd and 4wd, but front diff is not engageing. What would cause this. I plan on pulling it into the shop and looking at it this evening. Any tips would be helpful.

UPDATE::

Shaft appears to be engaged even with blazer off.

UPDATE::

Shaft appears to be engaged even with blazer off.

Update:
Pulled vacume line off the actutator under the battery and released pressure and the shaft is now disengaged. Is this normal to have pressure after its off? if I do have vacume, then why isnt the front diff enageing?

SO this is where im at right now, shaft is staying engaged all time and wont engage the front diff.......What gives what should I look at now???????????????????

alright, my bad

jacked up the front only to find that the front diff is engaged full time and the t-case is not engageing. So now what, I here the motor switching gears down there when I push 4hi and 4lo but tcase is not engaging. where do I go from here??

Look at the actuator in the front axle. It is apparently not locking in the side gear.

The front driveshaft may turn so long as there is no resistance at the front axle (gears not engaged). Engage 2HI and shut off the engine. With the vehicle OFF, can you turn the front driveshaft?

OKay this is whats happening.......

front diff is enaged so no I cannot turn the shaft, which I think is how it is supposed to be, if I pull the vacume line to the actutator the pressure is released and the front diff is disengaged, so then the shaft will turn freely. But when I put it into 4hi the t-case appears to be not enageing. Some times when it is in 4hi and I am spinnning the rear tires I can here that ratcheting sound from the t-case, its a noise like its not fully engaging, just rubbing teeth or something. As for 4lo it makes the clunk, and is geared down but once again t-case didnt engage the front shaft.

The NV233 selectable transfer case is used on your '98 Blazer. Both drive shafts are "live" at all times. They both turn simultaneously when the vehicle is in motion. The front differential is locked to power when the actuator is activated by changing the mode switch to 4HI. 4LO is accomplished when the encoder motor changes the gear range in the transfer case.

Put the mode switch in 2HI. Put the transmission in park. Raise both front wheels off of the ground. Leave the rear wheels on the ground. If you can turn your front drive shaft, (by hand) there is a problem in the transfer case.

My front passenger side axle is staying engaged, its getting vacume to the actuator even when in 2wd, even with it not running..... With the front wheels off the ground I can spin the front shaft but its also spinning the front passenger wheel. Meaning the tcase is not engaged. But you say that the front shaft is always engaged, but that is not the case because when it was functioning I was watching that shaft and it would turn when in 4wd but when in 2wd the shaft did not turn. I remember that from when I had vacume problems to the front diffrential about 1 month ago.

No surprise there. When you were in 4WD the actuator locked the axles to the drive shaft. In other words, the axles were powering the drive shaft.

No, see the vacume line fell off the actuatator so the front diff wouldnt engage at all, but when I hit 4 wheel the shaft would spin and when I hit 2wd the shaft didnt. So oviously that shaft isnt live all the time, only when in 4wd.

So I got a front driff with the passenger side axle enaged full time(actuator is engaged),and a tcase that wont engaged the drive shaft..So my front shaft is turning but its only because the front diff is locked in, in other words there is no power to the front wheels

The front driveshaft may turn so long as there is no resistance at the front axle (gears not engaged). Engage 2HI and shut off the engine. With the vehicle OFF, can you turn the front driveshaft?

So if I understand all your testing thus far, when the vehicle is on the ground, the engine is off, the transffer case selector is in 2HI with no vacuum at the front differential actuator, and you have verified that the actuator has mechanically released at the differential (no stuck cables), you can manually turn the front drive shaft? That might be a problem.

The "ratcheting" sound may be an indication of a stretched chain in the xfer case. How many miles are on the vehicle?

No, with the vechile on the ground in 2hi with motor off the front diffrential is staying engaged, the vaume is holding it, if I pull the vacume line, the front diff will release, I can then turn the front shaft. But the transfer case does not seem to be locking in because when the front diff is locked in the wheels wont spin, So I think that the vacume switch in the transfer case is stuck, that is why there is constant vaume to the front diff, but this doesnt explain the transfer case not engageing does it?

There is 157,000 miles on the beast............

Transfer case operation can get quite technical. I will keep this as easy to understand as possible, so that anyone that reads this, regardless of his or her technical aptitude, can understand it.

The NV233 selectable transfer case has a sprocket on the rear output shaft. The rear drive shaft is connected to that shaft. There is also a sprocket on the front output shaft. The front drive shaft is connected to that shaft. A chain connects the two sprockets so that both drive shafts rotate at the same RPM simultaneously. Any time the vehicle is in motion, both drive shafts, all four axle shafts, and both front and rear differential carriers rotate. The rear axles are both “locked” to the rear differential carrier at all times.

When you change the transfer case "Mode" from 2HI to 4HI, the vacuum actuator, located under the battery, moves a pin that locks the right front axle shaft to the front differential carrier and the front differential now becomes “live”, just like the rear differential.

When you change the “Range” from 4HI to 4LO the encoder motor, mounted on the transfer case, changes the output shaft gear ratio by changing to a different set of gears in the transfer case.

If the pin that locks the right front axle to the front differential carrier remains engaged after changing the mode to 2HI, (as with an actuator or cable failure) the vehicle will remain in 4HI. If the chain now fails between the two output shafts, the front differential carrier, front axle shafts and front drive shaft will still rotate as a unit. However, the assembly will not be “live”. Only the rear wheels will power the vehicle.

ok, the right front axle is staying engaged because the vacume switch bad, the ball is seized down, and the transfer case wont lock up that front shaft so does that mean the chain had failed????? Is that a easy fix or does the whole tcase have to come down, the chain must have been loose because I remember I could rotate that shaft before like 1 whole turn before it would stop. So this chain must be the problem.......fill me in on this..............

BINGO! Chain probably has too much slack, (stretched). Transfer case must be removed and disassembled. Several special tools involved to overhaul it. Might be best to look for a used one.

Depends what the problem is with the axle, there is a shift fork in there that may have failed. A visual inspection will tell you for sure what it needs.

More than likely the chain of events went something like this:
The actuator pin or mechanism failed and kept the axle locked, so you were in 4WD all the time. This caused undue wear on the chain weakening it. Shifting back and forth to get "unstuck" changed slack in the chain from one side of the sprockets to the other and stretched the chain.

Damn, how hard is it to remove the tcase and install a new one???

What should used one cost???? Are they all compatible with eachother or will it be a bitch to get them to match?

Best to check with a salvage yard, they can tell you what years will fit, and how much $$$. There were two different transfer cases used in '98. Selectable and automatic. 3 button selectable is what you have. Model is a NV (New Venture) 233. The job is labor intensive but not difficult. Better invest in a shop manual to help you through the replacement.

There is very little room to remove/install a transfer case in a '98 Blazer. The rear crossmember is a permanent part of the frame, and the transfer case needs to be turned, twisted, and manipulated out and back in.

http://72.19.213.157/files/TransferCaseDisconnectionLg.jpg

If you want a little better idea of what you're in for, check this page:

Driveline (http://72.19.213.157/files/4L60ERemoval.html)

As advised, a good repair manual is going to be invaluable.

So its not possible to remove the tcase and just replace the chain and reinstall.....

Why arent theses transfer cases just geared together, whats the point in the chain.

Yes, the chain can be replaced, but after you split the case apart, you will likely find more parts that are worn, sprockets, gears, bushings, bearings etc etc, and then there's the thing about needing the special tools and a GM shop manual for disassembly and reassembly. Chilton and Haynes do not cover transfer cases, and for a good reason. It's a rather complicated procedure; it’s not just a matter of take it apart and put it together. It's similar to rebuilding a transmission.

There are several reasons they use a chain. One is to get the distance between the input and output shaft that is needed. The front drive shaft needs to be tucked up along side the engine. If gears were used, they would need to be very large in diameter to obtain that same spacing. Using gears would increase the size of the transfer case, increase the weight, increase gear noise, and decrease ground clearance, to name a few.

I am getting ready to call it quits with the blazer, for the gas mileage I get I could be rollin bigger a nice truck. I guess this machine is getting tired and not to mention I brought it back from the dead. If this transfer case is to expensive I might just say screw it..........Either sell it or scrap it. I mean a 2wd drive blazer in Minnesota is pretty much worthless with out about 1000lbs of weight in the back:banghead: .................

But we will see I guess. . . . . . . . .

See this thread: http://www.automotiveforums.com/vbulletin/showthread.php?t=665595

Or this:

http://www.drivetrain.com/231transfercasesillust.htm

Or this:

http://www.drivetrain.com/231transfercasesillust.htm
That's an awesome exploded view, but I had actually posted the link so that he could see my description of the transfer case operation. In my experience, being able to turn the front drive shaft by hand when in 2wd is normal operation, and doesn't necessarily indicate a problem within the transfer case.

Problem is I put it into 4wd and that shaft still spins freely!!

Best to check with a salvage yard, they can tell you what years will fit, and how much $$$. There were two different transfer cases used in '98. Selectable and automatic. 3 button selectable is what you have. Model is a NV (New Venture) 233. The job is labor intensive but not difficult. Better invest in a shop manual to help you through the replacement.

Are you sure its a NV233 and not a NP233 I cant find a NV233 anywhere

Very interesting, the 1998 GM S/T truck shop manual second edition shows a NV233 selectable (3 button) transfer case being used in the T body and utility (Blazer) with the 4.3L engine. It also shows a NV136 automatic transfer case. It does not acknowledge the NP series anywhere. NV=New Venture NP=New Process. It also says the motor/encoder only changes the "range" (LO & HI). That may be one of the differences between the NP231 and the NV233. I'll do some research and post back my findings.

Very interesting, the 1998 GM S/T truck shop manual second edition shows a NV233 selectable (3 button) transfer case being used in the T body and utility (Blazer) with the 4.3L engine. It also shows a NV136 automatic transfer case. It does not acknowledge the NP series anywhere. NV=New Venture NP=New Process. It also says the motor/encoder only changes the "range" (LO & HI). That may be one of the differences between the NP231 and the NV233. I'll do some research and post back my findings.Yeah, those are the only ones that I see listed, too.

Found some info about the operation here:
http://books.google.com/books?id=j3-lFqKxbLkC&pg=PA83&lpg=PA83&dq=new+process+new+venture+233+transfer&source=web&ots=hQw73ijbv-&sig=q2uoNHtp7li3Sg746xSeqY5Zk_0#PPA83,M1

NP-231C/NV-233-Introduced in 1988, this part-time transfer case became the mainstay for the S-series trucks. It's quite a bitstronger than the NP-207C it replaced. Chain-driven with a 2.72:1 low range,it's reliable even with more than stock horsepower applied. A part-time setup with a centered rear output, the chain is only in operation when four-wheel drive is used, so it's a long-wearing T-case if the oil is changed with some regularity. The NP-231 is synchronized and the "C" versions of this T-case use the wider and stronger 1 1/4-inch drive chain, unlike the Jeep "J" version that uses the smaller 1-inch chain. The NP-231 has an oil pumpand is much better lubricated and cooled than the NP-207C it replaced. Many NP-231C units also use a six-pinion planetary gear and the rest use a four-pinion unit. The NV-233 is an electronically shifted version of the same gearbox that was optional starting in about 1992.


Some info about the NVG numbering system:
http://www.bc4x4.com/faqs/yj.cfm?cat=6&faqid=162

Also says "When in 4wd, front and rear driveshafts are locked together."

Are you sure its a NV233 and not a NP233 I cant find a NV233 anywhere

It might be worth a try to check for transfer case codes.
Ground pin 13 on diagnostic connector and see if shift lights blink any codes.

It might be worth a try to check for transfer case codes.
Ground pin 13 on diagnostic connector and see if shift lights blink any codes.
I agree. While the chain is still a definite possibility (especially considering the circumstances), I would investigate all other possibilities before condemning it. Including some of the simple things like reseting the TCCM by disconnecting the battery for a short period of time.

I though that New Venture is part of NPG, even after Magna bought it all out from GM and Daimler. ???

Can I get some better instructions on the method for pulling the codes???? What pin is 13? Ground right to the metal bracket? Fill me in!

paxfam1

Can I get some better instructions on the method for pulling the codes???? What pin is 13? Ground right to the metal bracket? Fill me in!

paxfam1


This link should show the pin no's on the diagnostic plug.
Link removed by poster
Jumper pin 13 and ground.
Turn key on and count the flashes on push button lights.
Post back any codes.
I think on that one you only get fro 1-2 3-4.
Also does the buttons light up right on push button shift?

Ok tried checking for any codes today and there was none. So I called my local salvage yard and they said they had a used one for 150 bucks. I think that sounds reasonable. What all is involved in dropping the the transfercase? Is there a how to some where or perhaps someone has a website that would be a bit of help to me. I am quite mechanically inclined I just want to no what im up for.............Thanks

See post #20 in this thread. There is a link that gives some good information.

"Used one" as in "used transfer case?"" A complete unit for that price is probably a good deal, so long as it's complete.

"Used one" as in "used transfer case?"" A complete unit for that price is probably a good deal, so long as it's complete.

Do you mean complete as in like encoder motor, vacume switch, ect..........

They just told me that they had a ton of them around and that a used one would be $150.

Quick question, in removing the t-case do you have to drop the tranny or can you just unbolt the tcase and remove it?

I havent started this project yet, but I am gonna drop the tcase tomoro night.

I dont have a manual, I really should buy one but dont have alot of extra money. Are there any websites online that have the same information?

Here it is, straight from the GM shop manual: Remove shield, remove drive shafts, (mark them before removal) remove vent hose, disconnect the electrical connectors from the 3 speed sensors, disconnect the electrical connector from the encoder/motor, support the transfer case with a jack, remove the bolts securing the transfer case to the transmission, remove the transfer case. Remove and discard the gasket, do not reuse.

Any idea what that gasket is called, or a number for it?

Thanks for the info sounds simple, whats the trick to removing the drive shafts?

Not sure, but I would imagine transmission output gasket, ask your parts store, they'll know. Gotta replace it, or trans fluid can leak into transfer case and eventually out the overflow and make a mess.

Rear shaft unbolts from rear differential and slides out of transfer case. Front shaft unbolts from front differential and you will have to "tap" it out gently to release the snap clip in the transfer case.

Do you mean tap out the clip or just tap out the shaft?

The clip is in the transfer case, just tap the shaft out. The word "tap" may be construed as a 3 pound sledge hammer may be necessary in some cases ;)

Alrighty, sounds good

Plan is to tear it off thursday night, so until then if anyone has any tips or info let me know. I think it will be easy but until I get started I wont no.

Thaks everyone for all the information.

P.s. Should I drain the the tcase before removal, and with the new one how much and what kind of fluid should I put in there

The skid plate will need to be removed from the case to allow clearance for removal. One of the skid plate fasteners has to be removed, while the others only need to be loosened since the mountings are only slots.

The transfer case needs to be tilted sideways, then twisted downward at the front to clear the transmission flange and the frame crossmember. There is almost not enough room to get it out. It's difficult to explain exactly how to twist it, but the interference points become

An articulated transmission jack is very helpful, since the case will start to feel heavy after a few minutes of turning and twisting to clear everything.

Be sure to get all the electrical connectors off the transfer case. There are a couple "hidden" ones near the top and right side. If my recollection is any good, there are four connectors. There is also a vent hose on the top which is usually just tossed up over teh transmission and tied on with a clip.

Did some final testing and I am convinced the chain is stretched to the max becuase, once in awhile when I shift I can hear that chain jumping teeth in the tcase. It seems to only catch a little bit while its in reverse, besides the little grinding its doing there is no power to the front. So tomoro I will drop that tcase, spit it open and inspect it, then put the used one in.

I asked earlier but I didnt get answers so I'll ask again.

Do I have to drain the fluid out when removing it? Should I change the fluid in the used one? What kind of lube does it need and how much.

Thanks all
paxfam

Probably be a good idea to drain the case before removal. It might save your arm pits from a fluid bath :). I would change the fluid in the replacement case also.

2.3 quarts of Dexron III automatic transmission fluid.

Good luck, better you than me! Keep us posted.

Wow, that was quite a job.

I dropped the tcase in about 3 hours, it went pretty well. The bolts holding on the tcase to the tranny were a reall bugger. The biggest problem I had was that very bottom bolt on the tcase the frame was in the way, I struggled with that for at least an hour. Then I got a bright idea to jack up the tranny, and wa la, that bolt was now easy removed. The part of acutally dropping it out of the truck was the easiest, I pulled it off the shaft and tipped it down and the weight caught my suprise and landed on my chest. Well that went well, we will see how install goes tomoro.

paxfam1

Ya got heat there eh? Mighty cold up there in Minnesota.

oh yea heated shop,

-11degrees faren.

New Tcase installed and 4x4 is working, install went well, the hardest part was coming up with that gasket, I ended up going to a dealer to find it. No parts stores stocked it nor could they order it. At first with the new tcase installed it really didnt want to come back out of 4wd, but I think its getting better as I exercise it more.

Weird thing is I went to put the fluid into it and from empty to full it only held like 1.3 quarts. I filled it, until it ran out of that second highest plug which I believe is the correct level.

And only other thing I notice is when its in 4wd its whining alot more then my old one, mainly at higher speed like 40-50 Not sure if cause it had not been used in awhile or what. Is that normal?

Tips for the future; have a full bottle of pain killers near by cause you will be living of them for the next day or 2.

Thanks all couldnt have done it with out you guys.

If that case was sitting for a while, it may shift easier as you use it more. You might want to double check the fluid level and be sure you used the upper most plug. If the case was empty, 1.3 quarts is not enough. Low fluid level will cause a whine. GM recommends using sealant tape on the drain and fill plug threads, and tighten them to 35 foot pounds of torque.

Did you split the old case open? What did you find? Glad to hear you're up and running again.

If that case was sitting for a while, it may shift easier as you use it more. You might want to double check the fluid level and be sure you used the upper most plug. If the case was empty, 1.3 quarts is not enough. Low fluid level will cause a whine. GM recommends using sealant tape on the drain and fill plug threads, and tighten them to 35 foot pounds of torque.

Did you split the old case open? What did you find? Glad to hear you're up and running again.

I am pretty sure I used the right plug, but I will double check cause I dont want to take any chances.

I did split it and found a chain that was stretched out really bad. Also the sprockets were rounded off from the chain grinding on it. The shafts also had alot of play in them, not sure if thats normal or if the bearings were shot.

The total cost for everything was like 175 (tcase,gasket,fluid) So I feel pretty good to have 4wheel drive again.

The old master has it covered. The only thing I would add is that even if the case had not been sitting for an extended period, drain and refill it again after some use. It will be cheap insurance. You might want to drive it gently for a while and wait until after northern Canada stops sending us their air. You might be a bit surprised at what drains out with the "new" oil.

IIRC, the torque specifications for the drain and fill plugs is cast into the case. Perhaps that's only on the New Process/New Venture units - I'm not positive.

I disagree. You could have done it yourself. It may have taken longer to gather the information, and you might have done a few things the hard way, but you would have finished it.

It will definitely be interesting to learn what you find in the old case.

I did split it and found a chain that was stretched out really bad. Also the sprockets were rounded off from the chain grinding on it. The shafts also had alot of play in them, not sure if thats normal or if the bearings were shot.

The "ratcheting" sound may be an indication of a stretched chain in the xfer case. How many miles are on the vehicle?

YES! Who's the MAN?! MIND-TAKING, baby! Stick with the Kid!

Meh, lucky guess. It could have very easily been a sprag, worn spline or a handful of other things. All we did was stand back, hold our beers, and point fingers. You did all the real work.


The total cost for everything was like 175 (tcase,gasket,fluid) So I feel pretty good to have 4wheel drive again.

$175 complete, and you really got a pretty good deal on the case. I looked at some used and re-man cases online, and you could have easily spent four figures. Add to that (or subtract?) the satisfaction of being self-sufficient. That's gotta be worth something, and may ease the pain a bit while your fingers thaw and the blueish-black color goes away.

:grinyes: I'm with Blue Bowtie, great job! Most DIYers wouldn't have the guts to tackle a job like that! :grinyes:

And the moral of the story is... If you get stuck, shift to LO range and slowly walk out. If you have to "rock it" back and forth, allow the drivetrain to come to a complete stop before changing gears. While slamming back and forth from drive to reverse may eventually get you "unstuck", the damage done to the entire drivetrain can be substantial, and costly.

Ya no, I am not sure if it makes the slightest diffrence but this tcase was out of a 96 blazer, would that make since to why it only holds 1.3 quarts at full?

1996 and up with a NP233 or NV233 transfer case all have the same capacity.