Driveshaft clunk

[debo4x4]

I just got my truck back from the dealer today and they said ther was no fix for the drivshaft clunk on reg cab trucks. Replacing the slip yolk is only for the ex cabs.  I'm really not sure if that is the problem or not.  You can only feel it when you let off the brake, and I feel a jerk.  I had a tech drive the truck with me and he felt the clunk but said they could do nothing about it now?  Any ideas?  I also asked to flash my pcm to recalibrate my spedometer and timing/fuel curve for the increased tire size but he said they have to take the entire dash off and send it in the be changed.  And that only changes the spedometer and something to do with the abs, not the timing or fuel curve.  I thought they could do all of that reprogramming at the dealer with the tech II.  Am I wrong?  I have had a good relationship with this dealer so I don't want to think they are jerking me around...

[badhammer]

they are only part right. the TSB to replace the yoke is only for the ext. cabs but they can put GM special lube in the yoke of your truck it works for about 8 to 10 months until it needs to be lubed again. I can get you the part number for it if you want it. also they can reprogram the speedo for the tire size with the tech two it recabralites the speedo and the abs system. they can not remap your fuel and Ing. this only GM can do or buy a hypertech programmer and do it yourself. they are blowing some smoke  your way though.

[HillHound]

Cheap way to try a fix yourself-drain and refill the transfer case and remove the yoke and lube the spline teeth with a good synthetic grease.  Total cost will be about $10 and 45 minutes of your time.

 

My Silverado was an ext cab Z71 and it developed the clunk/bump at about 5000 miles.  I did what I described above at 10000 miles and the problem was still gone when I traded it a year later at 25000 miles.

[alsz71]

I understand the grease on the spines ...could you explain why the draining and refilling of the transfer case.

[Dihappy]

Cheap way to try a fix yourself-drain and refill the transfer case and remove the yoke and lube the spline teeth with a good synthetic grease.  Total cost will be about $10 and 45 minutes of your time.

 

My Silverado was an ext cab Z71 and it developed the clunk/bump at about 5000 miles.  I did what I described above at 10000 miles and the problem was still gone when I traded it a year later at 25000 miles.

You dont have to grease up the teeth, most of the noise(if not all of it) comes from the outer part of the yoke as it slides in and out of the tranny.  

 

The back end usually developes a little rust and you can sand that smooth if you want.

 

Ive applied quality synthetic grease to the smooth outer surface of the yoke and cured it for 10 months on my truck. Im on the second greasing

 

As for the T Case fluid.  Some believed that changing the fluid to the GM purple stuff could also cure the slip yoke "squak" noise, but it didnt with mine.  

 

I had to lube up the yoke.

A new Nickel Plated Yoke is avail for the xtended cabs only i guess, and runs $212.00 but i have yet to purchase one.  The lube seems to work really well.

[artt]

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.

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