I'm getting a loud clunk that sounds like a bad u-joint when my tranny shifts 2nd to 3rd. It happens when it upshifts or downshifts and only between those gears. Also it usually only does it when shifting in the 1500-2500rpm and 30 to 40 mph.

I have checked the u-joints, inspected the diff and changed the fluid and pulled the shafts and lubed the splines. Also changed the tranny and transfer case fluid.

I took it to the dealer and drove around with their tranny mech and he didn't know what it may be. He just said GM engineers lots of clearances in the drivetrain on the 4x4's and said to try lubing the splines which didn't fix it. Also had the guy at the trans shop that changed the filter and oil listen to it and he didn't know. I ask him if the custom tune I have might have caused it but he didn't think so.

Any ideas? It is a 3.73 G80.

 

You have what everyone has to some degree. Mine still clunks a little even after a tranny rebuild and an Eaton posi being added. The dealer was right telling you about loose clearances in the GM drivetrain. All the pros I've talked to tell me the same things.

 

It's normal.....

Document ID# 1430424
2002 Chevrolet Chevy K Silverado - 4WD


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Information on 2-3 Upshift or 3-2 Downshift Clunk Noise #01-07-30-042B - (Jan 16, 2004)
Information on 2-3 Upshift or 3-2 Downshift Clunk Noise
2004 and Prior Light Duty Trucks

2003-2004 HUMMER H2

with 4L60E or 4L65E Automatic Transmission (RPOs M30, M32)

This bulletin is being revised to add the 2004 model year. Please discard Corporate Bulletin Number 01-07-30-042A (Section 07 - Transmission/Transaxle).

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.



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.


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Document ID# 1430424
2002 Chevrolet Chevy K Silverado - 4WD

 

Thanks ranwalk. I guess I can live with it but it sure is annoying. It really sounds bad. It only does it during part throttle shifts and is stop and go traffic. Will a shift kit and servos will that help or will a rebuild or upgrade to a 65E help?

 

A rebuild will only do so much. It is the use of the stock GM parts that makes up the stack up of all the slop in the transmission from component to component. Some good race transmission shops are working on resolving the clunk issues but if you can live with the noise the 4l60 transmission can be built to handle some serious power before having to go to a 4l80.
I got mine built my Automatic transmission design here in Wisconsin.
http://www.autotransdesign.com/motorsports/index.html
We will see how long it lasts after up my boost.

 

I'll just live with it I guess. I've been wanting to go FI for more towing power but I'm afraid of blowing up the stock 60E. Now that I know this is "normal" I won't worry so much about it.

 

Yup sure is normal found out at the dealer a way back ago! I still hate tough seems like the Trany is slipping.