What is the Clunk?

airtight_python · #1 10-15-2004, 12:15 AM

After breaking (not necessarily to a stop), and then accelerating again I hear/feel a clunk in the drivetrain. Would this be a u-joint or a transmission problem?

Mork · #2 10-15-2004, 05:04 AM

It's what GM calls "Norman Drivetrain Lash" :-(
The clunk I experience only occures when changing between 2nd and 3rd gears.

vnotaro · #3 10-15-2004, 10:08 AM

I've experienced the same clunk about 50% of the time since the truck was new (2001). GM has put out at least one TSB on this but I don't know the number. I never had any work done on my truck for this but a friend with a 2002 truck noticed it almost immediately and has had the dealer change the u-joints, driveshaft and also has had work done in the rearend itself. Nothing worked. The service manager at the dealership where I bought mine said that the "clunk" shouldn't affect the life of the drivetrain in any way. I've only got about 40k on it and so far it's only been annoying, but we'll see...

tbacon1 · #4 10-15-2004, 11:02 AM

99 Silverado, Auto Trans, 5.3L eng, 4WD

i've had a similar problem with the clunk in the drivetrain but mine does it just as i come to a stop and right as i accelerate. i've got 84k miles and it started doing it around 40k miles. everything still seems fine. had my transmission fluid flushed about 3 weeks ago and they didn't say anything when they inspected it before flushing it. i did read a technical service bulletin saying that i should replace the slip yoke (thing the u-joint connects to) with a nickel-plated slip yoke but some people here have said even that is only a temporary fix ... good for maybe 20k miles. also heard greasing it helps for a few weeks but will eventually begin to clunk again. we're just another unlucky customer that has to deal w/ a manufacturing default.

Nigel215 · #5 10-15-2004, 11:24 AM

Quote:

Originally Posted by tbacon1

99 Silverado, Auto Trans, 5.3L eng, 4WD

i've had a similar problem with the clunk in the drivetrain but mine does it just as i come to a stop and right as i accelerate. i've got 84k miles and it started doing it around 40k miles. everything still seems fine. had my transmission fluid flushed about 3 weeks ago and they didn't say anything when they inspected it before flushing it. i did read a technical service bulletin saying that i should replace the slip yoke (thing the u-joint connects to) with a nickel-plated slip yoke but some people here have said even that is only a temporary fix ... good for maybe 20k miles. also heard greasing it helps for a few weeks but will eventually begin to clunk again. we're just another unlucky customer that has to deal w/ a manufacturing default.

I have the same thing. It clunks only from a complete stop. But I only noticed if after I installed my exhaust. I donno if its just something not tight or if its the same thing you guys are talking about.

hayesbcajh · #6 10-15-2004, 01:34 PM

I've got a 2000 5spd with 93k miles on it. I got the truck with 60k and it has clunked since I got it. Had it looked at 3 times and same answer, "normal backlash". Changed the u-joints just in case but wasn't the problem. I don't mind the noise, just hate not knowing if I'll be stranded 100 miles from home.

deadmeat · #7 10-15-2004, 01:38 PM

Could this noise be coming from the slip yoke? I had a similar noise when slowing down and then resuming speed and the dealer regreased the yoke to clear it up. This was only a temporary fix though my clunk came back again after a while.

LT-Z71drvr · #8 10-15-2004, 09:01 PM

My 2000 does the same thing. I thought it was a caliper hanging up or something, but my calipers are fine. It only does it after accelerating from a complete stop.
You sure would think that GM could clear this up.
I have also been told it is nothing to worry about, but it is annoying!!!

airtight_python · #9 10-15-2004, 09:30 PM

You're right. Very annoying. Why should GM vehicles do it if other makes don't? GM is being gay with their excuses. Seems like my new Silverado has got more problems than my 1987 GMC S-15 ever did. I miss that truck.

LT-Z71drvr · #10 10-15-2004, 09:39 PM

Yeah, I feel the same way. I had a 1996 C/K 1500
with a 4.3 V6, and I NEVER had a single problem with
it. I only got rid of it cuz I needed more power for
pulling my travel trailer.

I am almost thinking of trading down!!!!!!!!!!!!!!

chuck16 · #11 10-16-2004, 12:26 AM

I believe that it is something to do with the 4WD System. From most of the posts here I gather that you guys all have 4WD's. My 2WD doesn't do this however, my 90' Blazer did it all the time. The only time i noticed it not doing it was when my 4WD was engaged. I think it has something to do with the way that the transfer case engages into the transmission but, I'm only summizing.
Anyways just some food for thought and my

worth.

airtight_python · #12 10-16-2004, 12:42 AM

Mine is 2WD. Does it mostly after stopping and then accelerating. Sometimes after slowing down quickly and laying back on the throttle.

gremlin96 · #13 10-16-2004, 06:19 PM

first thing i would check is the spair tire. some times the cable strechs. this will couse the tire to swing back and forth during stops and take offs.

if that does not work check all the cv joints, if you like thay are u-joints, for slaping. chevy does not install grease zerks on them and after time the bearings ware out. all thay care about is getting the truck thru the first 3 years or 36k miles.

TexasF355F1 · #14 10-16-2004, 08:10 PM

What about the clunk when shifting from Park? Is that the same thing?

LT-Z71drvr · #15 10-16-2004, 10:00 PM

Texas-
The noise is different, but I think the two problems are related.
Like when you shift from D to R, or vice versa.
I think that there is just that much play in the driveline.
It would seem to me that over time it would wear something
out...
I guess we'll see...
Might hafta go get a Ford!!!

LOL!!

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