Olds Bravada AWD problem


Moser97
07-02-2005, 01:36 AM
Hi all, I'm Larry and I'm brand new here. On advice form Olds forum regulars I am posting this here as well as on the Bravada page. I am buying a '97 Bravada with a bad shake in the drive train. My neighbor is a retired Olds mechanic and he drove it about a mile and said he is almost certain that the Smart Trak transfer case is malfunctioning. The vibration gets better at speed, almost disappears in turns, is not nearly as bad for a minute if you let the car sit and idle for a while. There is a chirping sound sometimes. My regular mechanic, a normally very competent guy, and my cousin put a new left front axle in today. The axle helped nothing. My neighbor said to change the transfer case fluid and replace it with the "blue" GM fluid for the smart trak system but the Olds dealer said the "97 doesn't take the blue fluid. It is a Borg-Warner case. We changed the fluid and put in Dexron lll. We are spinning our wheels here and need some advice. I am getting a very nice car at a great price so I will spend what it takes to fix it, I just need to know what to fix. I will post this on the other GM board as suggested below. Can anyone tell me where to go next here? Is there some where to buy the parts cheap? Can the guy who rebuilds our trannies rebuild this? (I will call him tomorrow.) Thanks in advance and Happy July 4 to all of you.

wolfox
07-02-2005, 02:15 AM
Change your transfer case fluid for the updated Alltrak-II synthetic fluid. Sounds to me someone may have filled it with Dextron-III and the fluid's burnt up and causing the shudder and lockup. 97+ years saw a revised forward clutch pack in those NP transfer cases used in on demand, and full-time AWD systems. It also affects AWD/SmartTrack Astro minivans and other "clones". These include Bravada, Jimmy and of course Blazer too. You have nothing to loose and all to gain on what may be a professional, technical error on the behalf of others. Swap for the blue and drive her a good 200 miles or so, drain and then refill with blue again. It will take out the burned up tar, no doubt on my behalf; that is sloshing in your transfer case at the moment. Once you fill her up again on the fresh blue stuff, you should be 100% okay. There is a TSB out on the matter and the consequences. Blazee may come up with the pertinent data for you, he's crazy good at that. :) Sorry to hear you already serviced the front differential tubes and axles, most likely it had little to nothing to do with the real heart of your problem.

blazee
07-02-2005, 03:01 PM
There is a TSB out on the matter and the consequences. Blazee may come up with the pertinent data for you, he's crazy good at that.

Swalt and TonyMazz beat me to this one:

Info - Improved Automatic Transfer Case Fluid #99-04-21-006
Improved Automatic Transfer Case Fluid
1999-2000 Cadillac Escalade

1998-2000 Chevrolet and GMC K/T 4-Wheel Drive Pickups and Utility Models

1999-2000 Chevrolet and GMC L Van Models

1999-2000 Oldsmobile Bravada

with Active Transfer Case (RPOs NP4, NP8)

Effective with vehicle production in late June of 1999, all active transfer cases on the above listed vehicles have been filled with Autotrak® II fluid, P/N 12378508 (P/N 10953626 in Canada). This fluid is a light blue color rather than the red color of the previous fluids and is the next generation Automatic Transfer Case Fluid. The fluid also contains a better friction modifier.

On the models listed above, the active transfer cases should only be serviced using P/N 12378508 (P/N 10953626 in Canada), even if the original fluid was the red Autotrak® fluid. The previous fluid and the new fluid can be mixed or topped off if necessary. The new Autotrak® II fluid will be the only available fluid once the supply of the old red Autotrak® fluid is exhausted on units older than stated above.

The Owner's Manuals and some service information will specify the incorrect fluid due to printing the information prior to the fluid change being introduced.

blazee
07-02-2005, 03:04 PM
Swalt beat me to this one, too.


Front Wheels Slipping with Vehicle in Four WHeel Drive (Replace Transfer Case Clutch Plates and Front Drive Axle Lubricant) #99-04-21-003B
Front Wheels Slipping with Vehicle in Four Wheel Drive (Replace Transfer Case Clutch Plates and Front Drive Axle Lubricant)
1999-2001 Chevrolet and GMC K and T Models (Silverado, Sierra, Blazer, Envoy, Jimmy)

with NV236/246 Transfer Case (RPO NP8)

This bulletin is being revised to correct a part number in the Parts Information section. Please discard Corporate Bulletin Number 99-04-21-003A (Section 04 -- Driveline/Axle).

Condition
Some owners may comment on a slipping type condition at the front wheels while the vehicle is in four wheel drive (4WD).

Cause
When the vehicle is driven extensively in low temperatures (-12°C (10°F) or below), slipping may occur when the vehicle is in the 2 HI mode. This occurs because the transfer case clutch pack does not have enough torque capacity to overcome the viscosity of the front axle lubricant. The friction generated by the slipping clutch discs may cause premature wear of the clutch pack assembly.

Correction
Overhaul the transfer case and replace the clutch plates on affected vehicles. Replace the lubricant in the front drive axle with synthetic axle lubricant, P/N 12378261 (in Canada, use P/N 10953455). Use the following procedure and the part numbers listed below.

Remove the transfer case drain plug. If the plug is difficult to remove or stripped, refer to Corporate Bulletin Number 99-04-21-001.
Drain the fluid from the transfer case. Refer to the Transfer Case sub-section of the applicable Service Manual.
Remove the transfer case assembly from the vehicle. Refer to the Transfer Case sub-section of the applicable Service Manual.

Important
The NV236 transfer case (T Models) uses 8 friction and 7 steel plates. The NV246 transfer case (K Models) uses 10 friction and 9 steel plates.


Overhaul the transfer case and replace the clutch plates. Refer to the applicable Transmission/Transaxle and Transfer Case Unit Repair Manual.
Install the transfer case assembly into the vehicle. Refer to the Transfer Case sub-section of the applicable Service Manual.
Install the transfer case drain plug. Tighten
Tighten the drain plug to 20 N·m (15 lb ft).


Important
Do not use standard DEXRON® lll fluid. Performance of the transfer case may be impaired.


Remove the transfer case fill plug. If the plug is difficult to remove or stripped, refer to Corporate Bulletin Number 99-04-21-001.
Fill the transfer case with 1.9 L (2 qts) of Automatic (AUTO- TRAK ll) Transfer Case fluid, P/N 12378508 (in Canada, use P/N 10953626).
Install the transfer case fill plug. Tighten
Tighten the fill plug to 20 N·m (15N·mlbN·mft).

Change the front drive axle lubricant to synthetic axle lubricant, P/N 12378261 (in Canada, use P/N 10953455). Fill the drive axle with 1.66 L (1.76 qts) for K Truck or 1.20 L (1.27 qts) for T Truck. Refer to the Front Drive Axle sub-section of the applicable Service Manual.

blazee
07-02-2005, 03:20 PM
I did find this though:

http://www.image-hosting.ws/direct/1604.jpg

http://www.image-hosting.ws/direct/1605.jpg

Moser97
07-02-2005, 03:24 PM
Thanks for the great replies guys. I just found out the car is a 1996 not 1997. From what I read above the fix is to rebuild the transfer case and then use the new fluid. Some folks have suggested changing it out and running a while to see if it gets better. The case is full of new Dexron lll now. I take it that is the wrong stuff all together. Will the synthetic fluid help the '96 model? Is there a commercial product available that I could get this weekend? The dealers are closed and I have this vehicle for the weekend. I am supposed to tell the guy if I want it on Tuesday. If I could find a fluid to use I'd change it out and take a little road trip to see if it helps. Thanks again, Larry.

blazee
07-02-2005, 03:31 PM
The problem requiring a rebuild is different than yours I only posted it because of the comment that Dexron III impairs the ability of the transfer case.

How positive is the guy that it is a problem with the transfer case? There are a lot of other things that can cause a vibration.

Moser97
07-02-2005, 07:10 PM
The guy is a 40 year Olds tech. He worked mostly on Subarus lately but said he's seen this lots of times. He has all the certs, all the schools. He retired in 2002. He says the only thing that gives him any doubt about what's going on is that the problem is worst going straight ahead at 15 to 25 mph and all but disappears in turns. I had it out for a while a little bit ago and noticed that it does not do it when it has been sitting still for a few minutes, whether it is running or not. Stop at Autozone and when you come out it will not do it in the parking lot at all and will go through 1st and shift before it starts. If it is moving a while it will do it at any speed. Thanks again for your help.

BlazerLT
07-03-2005, 05:08 PM
I think you should look elsewhere than the transfer case.

If the engine is vibrating at idle, chances are a motor mount is gone.

chcknugget
07-03-2005, 09:24 PM
I agree, I don't think the problem is the transfer case, but I would still upgrade to the autotrak II fluid because it's great.

Moser97
07-03-2005, 09:42 PM
I came up the hill past my neighbors today and he then walked over to my house and said he was not so sure about the transfer case after listening to it go by him. We found a broken left motor mount. I will replace that and it the problem still exists we will look at the other axle. His wife said we looked pretty comical driving around with the hood up trying to connect the sounds to the movement of the engine. I doesn't carry on backing up at all, so it might be just the motor mount. I'll let you know what we come up with. Thanks again for all the help.

rlith
07-04-2005, 07:36 AM
I came up the hill past my neighbors today and he then walked over to my house and said he was not so sure about the transfer case after listening to it go by him. We found a broken left motor mount. I will replace that and it the problem still exists we will look at the other axle. His wife said we looked pretty comical driving around with the hood up trying to connect the sounds to the movement of the engine. I doesn't carry on backing up at all, so it might be just the motor mount. I'll let you know what we come up with. Thanks again for all the help.

Might as well replace both of them.. Also when putting the new ones on, cut the lower ear facing the front of the truck off to make it easier to swap out in the future.

Moser97
07-10-2005, 12:30 PM
Hi guys. I could not access the forums for a couple of day. I don't know if they had a problem or me, but my shortcut would not work.

When we found the broken motor mounts I thought we were home free so I bought the car. It is no better now than when I first posted. The most puzzling thing here is that this cars is smooth as silk when cold and will not act up until it is warmed up completely, having been driven 10 or so miles. Before that there is a VERY small vibration no worse than the rumble from my '99 GMC 1500 PU when you run it in 4wd on dry roads. Once it is warmed up the problem starts. I found out it was driven for a while with a different model tire on after the guy got a flat. The problem started after a few days of running with this odd tire. The flat has been repaire and all the tires are now the same. I have seen advisories online that say a tire difference of .25" will destroy the transfer case clutch. Another puzzling thing is the problem is worst going straight. It is apparent sometimes in turns but not as bad. I've talked to quite a few guys in the last week about this and everyone says that doesn't seem right if the problem is in the TC.


SYMPTOMS
1. Bad shake when you pull out, classic clunking like bad U joint. Not nearly as bad when the car is cold or has been sitting a while. This is much worse going up hill. Gets better as you put on speed, but doesn't go away. It does not get better or worse if you swerve form one lane to the other.
2. Chirping sound like a dry bearing will make, again after warm up.
3. Sound like a fan blade hitting something. This is not all the time.
These symptoms go away like you turned off a switch if you let off the gas, will sometimes come back not so bad right before the car stops under braking. They get better in turns, even under acceleration in turns. Not present in reverse even under acceleration. At 60 MPH it settled down to a dull rumble.
So far we have done the following, none of these thing helped much if at all.
1. Changed left front axle.
2. Changed both motor mounts, (both were broken).
3. Replaced transfer case fluid with AutoTrak fluid from dealer. Have driven about 100 miles on this new fluid, with no change in symptoms.
4. Removed and inspected rear drive shaft, no problem found, greased all U joints and reinstalled.
5. Attempted to remove front drive shaft but couldn't because of stripped bolt.
6. Inspected rear cross member tranny mount found it in good condition.
7. Checked lug nuts, tire pressure confirmed all tires are same size and brand.

I am thinking I should burn off the bolt and pull front drive shaft and inspect it too. Maybel try to drive the car with the front shaft out and see what happens. I read that running without the shaft will kill the clutch also, but I am afraid it is already gone. I am waiting to see what some of you say before I do that. Once this starts, it feels like a bad drive shaft. We didn't change out the rear U joints because they look brand new and were all free and working well. So, then we should look to the front shaft, but why does it take 10 or 15 minutes for these symptoms to show up?

Help me out guys, what the heck is going on here? I have $325 in chasing this now. I don't mind paying to fix this I just want to fix the right thing. Some of you have said to focus somewhere besides the TC. Where should we look next? I trust these mechanics, they are careful and consciencious, and also family. We don't know what to try next. How can we check/test the front shaft? Will the shaft out of another S-10 type vehicle fit in this Olds? If the car runs smoothly with the shaft out where do we go from there? Is it OK to run the car with the shaft out? Why does it take 15 minutes for these symptoms to show up, if you start with a cold car. Any help or suggestion you can offer will be greatly appreciated. Larry M.

chcknugget
07-10-2005, 12:56 PM
SYMPTOMS
1. Bad shake when you pull out, classic clunking like bad U joint. Not nearly as bad when the car is cold or has been sitting a while. This is much worse going up hill. Gets better as you put on speed, but doesn't go away. It does not get better or worse if you swerve form one lane to the other.
2. Chirping sound like a dry bearing will make, again after warm up.
3. Sound like a fan blade hitting something. This is not all the time.
These symptoms go away like you turned off a switch if you let off the gas, will sometimes come back not so bad right before the car stops under braking. They get better in turns, even under acceleration in turns. Not present in reverse even under acceleration. At 60 MPH it settled down to a dull rumble.

My tranny made chirpping and grinding sounds when it went out, and even like a fan blade hitting something. I'm not trying to point you on a wild goose chase, but have you ruled out tranny problems?

Moser97
07-10-2005, 01:39 PM
Thanks for the reply. We have considered the trans might be out. Thats one of the reasons I would like to run it with the front shaft out. If the symptoms are still present that would suggest the trans as a problem. Did yours continue to run? Did it make the noises when it was cold? Is anyone familiar with the inside of this viscous clutch in the transfer case? If the shaft is out wouldn't the clutch just carry the front output portion of the case along for the ride?

Moser97
07-11-2005, 09:21 PM
Please don't tell me you guys are out of ideas. I asked my cousin what should be my next move and he said "First, pay me. Then see if you can find some fool to buy it from you".

rlith
07-11-2005, 09:25 PM
Please don't tell me you guys are out of ideas. I asked my cousin what should be my next move and he said "First, pay me. Then see if you can find some fool to buy it from you".

At this point I would take it to the dealer and let them do a diag on it (about 50 bux for an hour) and see what they say. Then fix it yourself.

greghartson
07-11-2005, 10:18 PM
replace all U-Joints

rksch
07-13-2005, 12:33 PM
This might sound silly, but I had this chinking noise which seemed to be located high up on the transmission near the torque converter. I had three shops look at it. Finally the transmission shop located the problem and determined that the starter was not fully retracting. It was floating and intermittently hitting the fly wheel and sounded like a metal part rumbling around. I believe the transmission shop had to open the access panels on the transmission to see the starter spindle not retract. I have not had any problem since replacing the starter.

Ralph

Moser97
07-30-2005, 01:42 AM
Well, I took the front shaft out and drove the car. If the shake was a 10 with the shaft in it was a 0.5 with the shaft out, but still there. My neighbor talked to his old boss who said quit fooling around and change the TC. I bought a 1994 Bravada with a bad engine on Ebay for $195. I emailed the guy and said I'd give him 50 more dollars to pull the trans, transfer case, and both drive shafts for me, then junk the rest. He agreed to pull the parts for me and get rid of the rest of the vehicle. I did a 12 hour work day, then a 400 mile road trip to pick the stuff up. He had lost the front drive shaft somewhere in the shuffle so I didn't get it. I took the existing shaft to a local shop that does drive shafts, springs and big truck service, and had it checked for straightness and balance. They also cleaned, inspected and repacked the CV joint on the shaft. $39 and the shaft was declared fit for service. If you have a problem with these this is probably the way to go, the guy said even if the CV was bad he still would have replaced it and got me back together for less than $100. Fortunately everything was OK. I had my cousin put the "new" transfer case and the shaft back in today. THE SHAKE IS GONE. There is still a little rumble at about 70 but the thumping and bumping from before is gone. I'll get the tire balance checked and probably get the shaft shop to do the rear drive shaft but you can drive the car and I kind of like it. The thing feels like it is binding up in the corners now so I'll do the transfer case fluid change out on it. My wife and I took it to dinner earlier, she says it rides like her Daddy's dump truck. I'm gonna drive it a while and either sell it or my 99 GMC Sierra Classic. I'm driving 100 miles a day and the 4WD, 5.7 truck is killing me on gas. I have a 17 foot boat to haul over a big PA mountain about every weekend so I will think long and hard before parting with the GMC. I have about $2400 in buying the Olds, and getting it to this point. I think I can make a few bucks on it, selling it. I am going to tear the old TC apart and see if I can see what is wrong inside. I really want to see how that thing works. If I see anything interesting I'll post about it. Thanks for all your help on this guys, and good luck with all those Baby Blazers.

Moser97
08-16-2005, 03:09 AM
The tire shop found a broken side wall in the tire that went flat originally on the other guy. He ran the odd sized spare for a week and killed the transfer case. I got 4 new 235x75-15's and it runs like a dream. I've got $2700 in it and have it in the local paper for $4400. My boss has a '99 Jimmy with 75K he wants to sell me for $5500. I think I'll take it and sell the pickup. Thanks again and good luck with these S-10's :iceslolan

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