Transfer Case Clunk

[Tim Z]

Guys, i have been tracking down a noise which i thought might be a U-JOINT but after laying under the truck today I rotated the Front Driveshaft back and forth and found the noise. It clunks in my T-case when i move the Front Drive shaft. Why is this and is it bad? What would it take to fix this? -Thanks

[foggy]

<div class='quotetop'>QUOTE(Tim Z &#064; Jul 30 2006, 01&#58;34 PM) [snapback]59387[/snapback]</div>

Guys, i have been tracking down a noise which i thought might be a U-JOINT but after laying under the truck today I rotated the Front Driveshaft back and forth and found the noise. It clunks in my T-case when i move the Front Drive shaft. Why is this and is it bad? What would it take to fix this? -Thanks
[/b]

Tim, drain your transfer case fluid to see if you have any shavings in it. You&#39;ll need Autotrac II fluid to go back in it.
Mine went out on me down at Allens last fall when he put my turbo on. It started out as a whine, then it started grinding real bad. Good luck.

[hummertech]

when in 2wd mode and moving the front drive shaft back and forth, the clunk noise is normal, i&#39;d check the fluid for sure, but i dont think that is abnormal. describe the noise in detail again please...

[Tim Z]

<div class='quotetop'>QUOTE(hummertech &#064; Aug 1 2006, 12&#58;42 AM) [snapback]59538[/snapback]</div>

when in 2wd mode and moving the front drive shaft back and forth, the clunk noise is normal, i&#39;d check the fluid for sure, but i dont think that is abnormal. describe the noise in detail again please...
[/b]

Thanks hummertech, i thought i read a lot of other guys having the same issues. Its just a small clunk but any noise bothers me. It doesnt do it all the time, It just seems to do it maybe when it shift s at a low speed say from second to third. You know, im just driving easy and when it shifts sometimes there is a clunk, which i thought was coming from sloppy U-joints, but they are tight. truck has 39,000 miles on it. I dont beat on the 4x4 system at all, ive only done say 5 4x4 street launches and i hit 2 wheel right after it shifts into second. Thanks for your advice you 4x4 guru&#33;&#33;

[hummertech]

yo, man, read this. i dont know how much you have played with the trans programing but this might help.


Document ID# 1656286
2005 GMC Truck GMC K Sierra - 4WD


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Subject: 4L60-E/4L65-E Automatic Transmission 2-3 Shift Clunk (Reprogram Powertrain Control Module (PCM)) #05-07-30-012 - (05/09/2005)



Models: 2005 Cadillac Escalade

2005 Chevrolet Avalanche, Silverado, Suburban, Tahoe

2005 GMC Sierra, Yukon

with 4L60-E (RPO M30) or 4L65-E (RPO M32) Automatic Transmission




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Condition
Some customers may comment on a 2-3 shift clunk noise. Typically, this clunk noise is most noticeable when the 2-3 shift occurs under approximately 48 km/h (30 mph).

Correction
Important:

• The PCM calibrations may REDUCE but not ELIMINATE the 2-3 shift clunk.

• This bulletin only applies to the 2005 model year vehicles listed above.

• As always, make sure your TECH 2® is updated with the latest software version.


To determine if this calibration will help to reduce 2-3 shift clunk, use the Tech 2 to navigate to the transmission diagnostic section and view the 2-3 shift adapt cells.
• If the 2-3 adapt cell values are negative, this calibration change will have minimal benefit in reducing the 2-3 shift clunk.

• If the 2-3 adapt cell values are above approximately + 5 psi, this calibration may provide a reduction in the 2-3 shift clunk.

Important: These calibrations also contain the second gear start correction as detailed in bulletin 05-07-30-013.

Technicians are to reprogram the PCM with an updated software calibration. This new service calibration was released with TIS satellite data update version 5 or later available May 1, 2005. Refer to Service Programming System (SPS) in Vehicle Control Systems in the appropriate SI Document.
Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

J6355
Module, Powertrain Control - Transmission Reprogramming
Use Current Published Labor Time




GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© Copyright General Motors Corporation. All Rights Reserved.



5 minutes later i found this also, thats gm for you.....




This bulletin is being revised to add the 2007 model years and include passenger cars. Please discard Corporate Bulletin Number 01-07-30-042C (Section 07 - Transmission/Transaxle).


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Important: For 2005 model year fullsize utilities and pickups, refer to Corporate Bulletin 05-07-30-012.

Some vehicles may exhibit a clunk noise that can be heard on a 2-3 upshift or a 3-2 downshift.

During a 2-3 upshift, the 2-4 band is released and the 3-4 clutch is applied. The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This same torque reversal can also occur on a 3-2 downshift when the 3-4 clutch is released and the 2-4 band applied. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case.

This is a normal condition. No repairs should be attempted.

[Tim Z]

Wow, thankyou for that great info hummertech&#33;&#33;&#33;&#33;&#33; I appreciate all that typing. So i guess there is nothing i can do about it except live with the "sometimes" that it does it. Im not sure if any programming will help due to the fact ui have a built trans/ shift kit and i dont want to take away any performance.??