[Olivier02]

Hi

I have had a problem with my 4wd for about 2 years. It started when I changed my encoder motor to a brand new one (dorman). My rear tires began to spin when I was turning (left or right). My mechanic told me that it showed that it was working now. and not before. There was something that wouldn't disengage and my differential was forcing. Last week, I changed the whole transfer case (TNT transfer case rebuilt), I had the rear differential oil changed (everything is fine, nothing broken inside), I had the discs changed , pads and caliper on the 4 wheels as well as the pedal break pads. I also changed the 2 CV joints. All brand new. Unfortunately, randomly, it may still have the same problem! Sometimes, it went back to doing the same thing. I turn left or right and he steers. I press on the accelerator pedal and I feel strain. The rear wheels spin. I do not know what to do. Most of the time, it works correctly, but with 4500$ spent, i want my problem to be fixed for good. Could it be a sensor abs problem? We read a code on the right front wheel yesterday.

thanks a lot.

 

[markmitch]

Please put your year info, so we know which transfer case you have-there were two used over the years. Thank you

 

[CopperFiremist]

Throw a couple front speed sensors at it

 

[AstroSurf]

Did you use Auto-Trak II ?

My old transfer case did the same thing without it. Now, I'm in RWD (NP236 t case) most of the time, and it doesn't happen.

echnical Service Bulletin.

Transfer Case Shudder (Flush and Replace Transfer Case Fluid) #99-04-21-005B - (Sep 10, 2002)
Transfer Case Shudder (Flush and Replace Transfer Case Fluid)

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.

o 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.
o 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.
o 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.
6. If this procedure does not correct the shudder condition, please call the Technical Assistance Center for further instructions.

Parts Information

Part Number

Description

Qty

12378508 (Canadian P/N 10953626)

AUTO-TRAK II Transfer Case Fluid

4 (1 L) containers

 

[Olivier02]

Please put your year info, so we know which transfer case you have-there were two used over the years. Thank you

NP136

GMC SAFARI 2005

 

[Olivier02]

Throw a couple front speed sensors at it

What do you mean?

 

[Olivier02]

Yes he used AUTO-TRAK II Transfer Case Fluid with the reconditioned Transfer case (np136)

Also, he is a transmission garage. So more experience. I did change the fluid of my old transfer case 3 times and it got better but ver not perfect. So with brand new oil in the rear axle and brand new oil in the TC, i still need other solutions.

 

[dchan51360]

Do you know if you have Limited slip diff's Just checking all the boxes for configuration.. I have trutrac's in my van.

Also encoders are finicky I went through 3 dorman and others before I paid the extra to get an OE AC Delco PRO encoder.. My similar symptom has now gone away. Every so often when I let the fluids go too long, I do get a little bit of gentle binding.. An autotrak flush and figure8's usually cleans it up.

 

[Olivier02]

Well, as i read you, it could be my encoder motor... Because the oil is brand new in the new transfer case and in the rear differential (wich is in good condition). And like i was saying, most of the time, everything works fine!

Brand new Transfer case with new oil (TNT Transfer case)
Rear differential inspected (no broken parts) with new oil
4 calipers,discs,pads,etc
2 cv joints brand new
New encoder motor (~16 months old) (Dorman)
My mechanic = more than 35 years of Transmission rebuild.


So my last bet would be the Encoder motor ?

 

[MechBob]

You may try a different encode motor, also look for corrosion on the TCCM connector,
BUT, what Copper has said.
The apply is controlled by the front speed sensors,and the rear one.
However, different tire diameters, speed, speed of turning the steering wheel can cause a harsh condition also. A bit of "bind" in these is usually normal, but not all the time.

 

[Olivier02]

Do you know if you have Limited slip diff's Just checking all the boxes for configuration.. I have trutrac's in my van.

Also encoders are finicky I went through 3 dorman and others before I paid the extra to get an OE AC Delco PRO encoder.. My similar symptom has now gone away. Every so often when I let the fluids go too long, I do get a little bit of gentle binding.. An autotrak flush and figure8's usually cleans it up.

Can you tell me what were the symptoms of the 3 dorman? Light on the dash, code, etc.

Because it is still under warranty and i need a reason to make an exchange. Thanks a lot

 

[Olivier02]

You may try a different encode motor, also look for corrosion on the TCCM connector,
BUT, what Copper has said.
The apply is controlled by the front speed sensors,and the rear one.
However, different tire diameters, speed, speed of turning the steering wheel can cause a harsh condition also. A bit of "bind" in these is usually normal, but not all the time.

Ok thanks. Do you know why it could have corrosion since the module is inside the van? Also, the speed sensors are the abs sensor too? Do they use (share) the same wiring? Finaly, my 4 tires are Nokian's. Same everything. But they are worn out differently. I dont understand because i made the tire rotation every oil change and my van is aligned.


Thanks

 

[AstroWill]

Also, the speed sensors are the abs sensor too?

No, they have zero to do with each other. The front wheel speed sensors have nothing to do with the AWD. There are two prop speed sensors that the TCCM looks at to determine slip for the AWD.

What happens if you completely remove the encoder motor and drive around, does it change your issue?

It helps if you put your year/make/model/engine/AWD/conversion/etc in your profile or signature line so we know what we are working with now and in the future. So much easier than having to go search for it. https://www.astrosafari.com/account/signature

 

[Olivier02]

No, they have zero to do with each other. The front wheel speed sensors have nothing to do with the AWD. There are two prop speed sensors that the TCCM looks at to determine slip for the AWD.

What happens if you completely remove the encoder motor and drive around, does it change your issue?

It helps if you put your year/make/model/engine/AWD/conversion/etc in your profile or signature line so we know what we are working with now and in the future. So much easier than having to go search for it. https://www.astrosafari.com/account/signature

Hi

I didn't tried to remove the encoder motor. I will try to remove it though. But Techbob and Copperfiremist said to look at the Frt speed sensor? If my TCCM was bad, would i had a code or something on the dash?

Also, all my informations are up to date since a very long time ( year/make/model/engine/AWD,etc). I don't understand why you don't see it.

GMC SAFARI 2005 SLT AWD

 

[gwd]

If you pull out the ATC 20 amp fuse to off the transfer case, does it still shudder?

 

[MechBob]

Will is right on the speed sensors, I was thinking of a different vehicle, sorry.

 

[dchan51360]

The bad encoder motor in one instance "locked" the transfer case. No errors but taking off in a straight line felt like someone had their foot on the brake for an instant before a short period of time then let go. Also shudder going around turns.

The second bad encoder was an error code and no AWD (put the vehicle up on a rack and front wheels did not "engage or spin at all"

 

[Olivier02]

Ok Perfect. Because Most of the time, it works fine now! With every new parts and oil, i saw a very big improvment. 9 times on 10, it turns smoothly. It is just that with all my efforts and money to put my awd back on track, i was hoping that it was flawless. It is very very frustrating to buy a new Transfer case, autotrak2 oil, cv joints, brake, caliper, encoder motor, etc and driving around town days later, park, and when trying to exit with difficulties. Again, it is some isolated case but still.

I removed the 20a ATC fuse. I dont know what to expect though? What do i need To look or feel and what is the conclusion?

Again, thanks a lot for your help

 

[Holiday]

Check your tires. The smallest variation of tire tread depth with these AWD systems (that are working correctly) will cause problems.

I have a 2005 Astro AWD. Went crazy chasing binding problems when I first bought the van. It had all sorts of issues including the PO putting the red transfer case fluid in it, and a bad encoder motor. Fixed both of those but was still getting some binding when parallel parking and tight turns. Was about to pull the transfer case and rebuild it until I came across a couple articles that solved my problem. The variation of my tires tread depth was too much, about 2/32 from the front and rears and was causing the awd to occasionally bind on turns. 4 new tires and no more binding, needed them anyway.

links to both articles:
http://tcase.rsgear.com/articles/2004_10.pdf

http://tcase.rsgear.com/articles/2007_12.pdf

 

[Olivier02]

I think you found the problem/solution!!!

My 4 tires are Nokian 215/70r16 WRG4 SUV. Bought them 3 years ago. 35 psi on 4. The thread have excessive Inegal wear! They are worn out completely differently! I need to change them anyway!

I will give you updates.