Latest info on clunking sound

bbviper · February 9, 2003

Whats the latest remedy for the clunking sound in the rear drivetrain. M 00 Sierra is experiencing this problem.

2000 GMC · February 9, 2003

My '00 Sierra was doing the same thing. Dealer took care of it under the warranty. If yours is still under warranty they should take care of it.

bbviper · February 9, 2003

my warranty just ran out, what was wrong with it? ???

Shaners · February 9, 2003

Most people have found the clunk to be caused by the driveshaft yoke. However some have cured the problem by replacing the universals.

I would try to grease the yoke with a good water proof grease to keep it from sticking. It's too bad there isn't a zerk fitting there so that it could be greased with regular maintenance.

2000 GMC · February 10, 2003

I forgot to answer it but Shaners did. If it was me I would give the dealer a call, you never know, they might take care of you.

99silveradoz71 · February 10, 2003

Driveline clunk has been documented extensively. I had the u-joints on my truck replaced around 20k I believe. The yoke was also greased a few times, then finally replaced. I switched the t-case fluid out last fall. No noise since the nickel yoke fortunately.

artt · February 10, 2003

There is another cause of the CLUNK. The TSB is below.

Some knowledgeable sources have told me it caused by the "crush sleave" in the rear-end. In order to assemble a rear-end without having to have an assembler make a measurement of the pinion to ring-gear lash, then select a shim to go behind the pinion before the shaft goes through the bearing, a crush sleave is inserted to collapse a fixed amount. The first time the rear-end fully loaded the pinion moves away. For racing purposes the gear lash is measured and a sleave is machined to fit and the ring-gear is smimmed.

They have repeatedly declined to fix mine, '01 1500 RC LB 3.42 w/locker.

They hope it last long enough to get past warranty!

Info - Driveline Clunk #99-04-20-002A

Driveline Clunk

2002 and Prior Light Duty Truck Models

This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 99-04-20-002 (Section 04 -- Driveline/Axle).

Important

The condition described in this bulletin should not be confused with Driveline Stop Clunk, described in Corporate Bulletin Number 964101R (Chevrolet 92-265-7A, GMC Truck 91-4A-77, Oldsmobile 47-71-20A, GM of Canada 93-4A-100) or Bump/Clunk Upon Acceleration, described in Corporate Bulletin Number 99-04-21-004.

Some owners of light duty trucks equipped with automatic transmissions may comment that the vehicle exhibits a clunk noise when shifting between Park and Drive, Park and Reverse, or Drive and Reverse.

Similarly, owners of vehicles equipped with automatic or manual transmissions may comment that the vehicle exhibits a clunk noise while driving when the accelerator is quickly depressed and then released.

Whenever there are two or more gears interacting with one another, there must be a certain amount of clearance between those gears in order for the gears to operate properly. This clearance or freeplay (also known as lash) can translate into a clunk noise whenever the gear is loaded and unloaded quickly, or whenever the direction of rotation is reversed. The more gears you have in a system, the more freeplay the total system will have.

The clunk noise that owners sometimes hear may be the result of a buildup of freeplay (lash) between the components in the driveline.

For example, the potential for a driveline clunk would be greater in a 4-wheel drive or all-wheel drive vehicle than a 2-wheel drive vehicle. This is because in addition to the freeplay from the rear axle gears, the universal joints, and the transmission (common to both vehicles), the 4-wheel drive transfer case gears (and their associated clearances) add additional freeplay to the driveline.

In service, dealers are discouraged from attempting to repair driveline clunk conditions for the following reasons:

Comments of driveline clunk are almost never the result of one individual component with excessive lash, but rather the result of the added affect of freeplay (or lash) present in all of the driveline components. Because all of the components in the driveline have a certain amount of lash by design, changing driveline components may not result in a satisfactory lash reduction.

While some owners may find the clunk noise objectionable, this will not adversely affect durability or performance.