So I've got this strange clunking sound that occurs from time to time. it doesn't bother me, but some people that i live with are getting a bit annoyed.

It's coming from the rear end (I think) and happens immediately after I put the truck in drive or reverse. It also happens as soon as I hit the brakes... but slightly different.

ideas? I'm thinking u-joints

 

U-joints are the first thing that comes to me but as you know it could be the rear end also. I have crawled under the truck and let someone shift from drive to reverse and try to see where the slack is. Good luck.

 

A 1998 ??? Could be your rear diff has develop some slop.
Like SlimJim said... Get somebody you trust to hold the brake and shift from D to R while your laying onder the truck, watching and listening.

Let us know what you find.

 

Definetly check out the u-joints, that could be the easiest fix to the problem

 

i would suggest to check your rear diff fluid as it may be due for a change and if its low fill it with the proper fluid
i think your diff has a fill plug on the front somehwere by the input shaft yoke
but deffenetly check the u joints first

 

I think I know this one! It may be that the front driveshaft yoke on my 2007 Silverado needed lubrication. The clunk drove me crazy! I took it to the dealer and (the second time) they took the driveshaft out, lubed the splines and put it back. That's the way that I understood it. Anyways, we had 3 similar trucks, all doing the same thing, and now that we knew what the problem was, our shop mechanic fixed them all.

 

Grease your tailshaft coming out of your tranny. They tend to bind. What you are describing is the same thing my dad's 90 model did. We removed the driveshaft greased it up real good and fixed it. My 90 model did the same thing, but the tranny rear mount was busted. Replaced it and also while I was at it greased the shaft splines and walla! No more issues.

 

I solved it!!!!

So I jacked up the rear end and played around with it for a few hours and couldn't find the play... I could wiggle the tires and it would move about a half inch in either direction before it caught on the drive shaft when it was in park... which is actually pretty good for a chevy I think. So I tried shifting from D to N to R and back and forth with the rear end jacked up and couldn't get it to do anything out of the ordinary. So I set it down and did the same shifting pattern to also try and replicate the infamous clunk... I tried everything and finally gave up.

As I went to back it out of the garage I put it in R and hit the gas... CLUNK. Turns out that it clunks when ever the rear end either drops or raises because of acceleration or braking. It's all because of the drivers side leaf spring that sags lower than the passenger spring and just barely rubs on the overload spring. I wrapped the two ends of the overload spring in duct tape and no more problem!

How stupid is that?!?!?

 

Good Job! Now what are you going to do to fix it once the duct tape wears through? Just curious as to what would be the next step.

 

Wow ... I would have never guessed. WHat caused that?