2002 Bravada AWD won't disengage...

[MyPsycho5Oh]

I was wondering if anyone has had this problem and what they might think it could be. Does the AWD engage using a speed censor. If so could it be a faulty censor that is causing the problem.

[khutchinson22]

what symptoms are you noticing? i am having a problem with my awd and im not sure what may be causing it.

[maxwedge]

There is a TSB concerning this problem including reprogramming the pcm and possibly replacing the transfer case encoder, check with a Chevy dealer, or GMC.

[Chris Stewart]

Some folks are getting some relief by changing the transfer case oil.

Hey Maxwedge, you'd love to do what I've been doing lately...I pocket ported a pair of INDY Cylinder Heads HEMI's, flowed'em and port matched the dual carb-single plane intake too. Real nice looking stuff going into a street rod.

[khutchinson22]

i just had jiffy lube change the transfer case fluid and the problem persists. what fluid are they supposed to use? im hearing something about a blue fluid that should be put in there. all they used was dex. mine is a 2002 as well.


also, where can i find the TSB listed?

[Chris Stewart]

Here's something from Chcknugget.

chcknugget []
AF Enthusiast



Joined: Oct 2004


Status: offline
Posts: 749

12-02-2004, 10:15 AM Re: smart trac help (Post #15)
It's actually not an additive like I thought, it's the actual fluid that goes goes into the case. It's a "blue colored fluid" called AUTO-TRAK II.

I found this in a the astrovan forum and thought it might be of some interest, however your car is a different year and I'm pretty sure its case uses different fluid anyways (check and see if you have the same transfer case p/n).

Bulletin No.: 99-04-21-005B

Date: September, 2002

TECHNICAL

Subject:
Transfer Case Shudder
(Flush and Replace Transfer Case Fluid)

Models:
1999-2003 Chevrolet Astro (AWD)
1999-2003 GMC Safari (AWD)
1999-2001 Oldsmobile Bravada
with All-Wheel Drive (NV136) Transfer Case (RPO NP4)

This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 99-04-21-005A (Section 04 - Driveline Axle).

Condition

Some customers may comment about a vibration (shudder) during tight turning maneuvers on dry pavement at vehicle speeds less than 8 km/h (5 mph).

Cause

This condition may be caused by a slip-stick of the clutch plates in the transfer case clutch pack. On 1999 and newer models, the preload that is designed into the clutch pack may contribute to the condition. In addition, contamination of the fluid may interfere with the friction modifiers.

Correction

Flush and replace the transfer case fluid on affected vehicles using the following procedure and the part number listed below.

Perform the following diagnosis prior to flushing and replacing the transfer case fluid in order to properly identify the shudder.

Diagnosis

1. Verify the shudder in the vehicle. The vehicle needs to be at operating temperature (driven at least 5 miles) for proper diagnosis. After the vehicle is at operating temperature, drive in a tight circle just short of steering wheel lock, at a speed less than 8 km/h (5 mph) in order to identify the shudder.

2. Identify what rear axle type the vehicle has.

^ If the vehicle has a standard rear axle, then proceed to step 3.

^ If the vehicle has a locking rear axle, remove the front propeller shaft. Refer to the Propeller Shaft subsection in the Service Manual. Drive the vehicle as outlined in step 1.

^ If the shudder goes away, install the front propeller shaft and proceed to step 3. Refer to the Propeller Shaft subsection in the Service Manual.

^ If the shudder does not go away, the locking rear axle may be the cause. Review the owner's records and determine if the rear axle was serviced at the first scheduled oil change. If records indicate that the axle service was done, then revaluate the condition using diagnostic information in the appropriate Service Manual. If the rear axle was not serviced, service the rear axle.
INFORM THE CUSTOMER THAT THE AXLE SERVICE IS AN OWNER'S MAINTENANCE ITEM NOT COVERED UNDER THE VEHICLE'S WARRANTY.

^ Install the front propeller shaft. Refer to the Propeller Shaft subsection in the Service Manual.


3. Flush the transfer case with the blue colored fluid (AUTO-TRAK II) using the procedure and part number listed below. Perform the flush procedure even if the transfer case contains the blue colored AUTO-TRAK II fluid in order to remove any possible contaminants. The AUTO-TRAK II fluid contains an improved friction modifier that should correct the slip-stick condition. Refer to the Transfer Case subsection in the Service Manual for information on draining and filling the transfer case.


Flush Procedure

Important :Refer to Corporate Bulletin Number 99-04-21-001, dated April 1999, for important information on removing the transfer case drain and fill plugs.

1. Drain the transfer case fluid.

2. Refill the transfer case with 2 L (2 qts) of new fluid, P/N 12378508 (Canadian P/N 10953626).

3. After refilling the transfer case, drive the vehicle a minimum of 8 km (5 mi).

4. With the transfer case at operating temperature, drain the transfer case fluid again.

5. Refill the transfer case with new fluid.

Important :The vehicle may require approximately 160 km (100 miles) of driving before the condition is completely corrected.

[MyPsycho5Oh]

Thanks i will try to flush and fill with the proper fluid as well as change rear diff. gear oil. I checked that stuff and it is really crappy looking. I have heard of GM products having problems with rears becasue of the gear oil they are usnig in some of the newer model vehicles.

[khutchinson22]

so i ended up just pulling the fuses and everything works fine now. i am going to take the car back in to jiffy lube so they can put the correct fluid in. hopefully that will help. i cant imagine that it would be anything else.

if the fluid doesnt solve the problem is there another possibility?

[maxwedge]

Yes there is also aanother tsb for the problem referring to reprogramming issues and/or replacing the encoder motor in the transfer case.

[maxwedge]

Yes, there is also another tsb for the problem referring to reprogramming issues and/or replacing the encoder motor in the transfer case.

[khutchinson22]

Originally Posted by maxwedge

Yes, there is also another tsb for the problem referring to reprogramming issues and/or replacing the encoder motor in the transfer case.

is that an official recall? where can i find the tsb?

[khutchinson22]

had the fluid flushed today with the proper Auto-Trac II fluid from GM. i put the fuses back in so the AWD system would come back on. The problem is still there but not quite as bad as before. When i say not quite as bad, i mean there is VERY little difference but it is noticeable. The TSB says you should drive the car ~100 miles to clear the entire problem but i am seeing that some people on this board have expierienced the problem clearing up immidiately, or, at least that is how it seems.

Any further suggestions? i have only put 35 miles on the flush but if the problem has taken time in other cars i will continue to be patient. i just dont want to screw up something else that could be quite costly.

thanks again for all your help!

[maxwedge]

Not a recall, tech bulletin, check alldata.com for the general descriptiopn, but any GMC, Chevy dealer can help you.

[maxwedge]

Not a recall, tech bulletin, check alldata.com for the general description, but any GMC, Chevy dealer can help you.

[khutchinson22]

Originally Posted by MyPsycho5Oh

Thanks i will try to flush and fill with the proper fluid as well as change rear diff. gear oil. I checked that stuff and it is really crappy looking. I have heard of GM products having problems with rears becasue of the gear oil they are usnig in some of the newer model vehicles.

how is your project comming? have you changed the fluid out yet? what were your results?