1999 Bravada Frontend Noise

[buckster496]

I just purchased a 1999 bravada with smart trac or whatever it is called. everything seemed good. now I have drove it for several days and now I am getting a noise,sounds like something is binding in the left front wheel area. it sounds bad. is this something to do with the 4 wheel drive? I jacked up the left front and everything seems fine. the tire will not spin though ,it acts as if the 4 wheel drive is engaged.is it suppose to be engaged at this point. didn't have it started. I did notice that it also turns the driveshaft to the transfer case. this is while in park. irt does turn freely, acts like it is locked as I would think the rear would be with the vehicle on park. whats wrong and what do i need to do?
thanks
Mike

[buckster496]

Come on experts, I am getting worried now. I pulled the atc fuse like i had read on here. the problem seemed to go away. but it didn't. I have not changed the transfer caese fluid as of yet. but it seems like it is 4 wheel drive all the time.I jacked the front up and tried to turn the left front wheel and it won't. it seems like it is locked into 4 wheel mode.maybe it is suppose to do this? but now it seems to be getting worse. it does it going away from a stop or turning and seems to come from the left front. it has a cachunk type noise that is speed oriented. and then it seems to go away at speed. what do i need to check before I really tear something up???? Take to the dealer? it is a 99 with smart trak.
give me some things to check.
Mike

[Chris Stewart]

Here's something from Chcknugget....



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.

[buckster496]

Chris,
thanks for the article, I will definitly try this first. Is this a service bulliten right from oldsmobile? I am going to change all the fluids since I just recently purchased this vehicle. that way I know where everything stands.
thanks
Mike Buchwald

[Chris Stewart]

I don't know if it's Olds or GM but a coupla people have posted good results from this procedure.