Rear end clank/clunk

tlocus · May 1, 2005

Hi,

I know it's hard to diagnose noises but just wondering what are some things I can check.

It doesn't happen all the time. It's when the rear wheels hit the bump, sometimes I get a 'clank' sound (between a clank and a clunk).

I know it has to be in the rear somewhere because it doesn't make the sound when the front wheels hit the bump.

thomas

snoman · May 1, 2005

Hi,
I know it's hard to diagnose noises but just wondering what are some things I can check.

It doesn't happen all the time. It's when the rear wheels hit the bump, sometimes I get a 'clank' sound (between a clank and a clunk).

I know it has to be in the rear somewhere because it doesn't make the sound when the front wheels hit the bump.

thomas

<{POST_SNAPBACK}>

Is it doing it under power where as the tire may be boucing airborne for a split second and the drive train troque is unloading and loading and you are hearing the slop get picked back up? My K3500 will do it sometimes when light loaded on bumps when braking as the wheel "hops" a bit.

GM-Tech · May 1, 2005

Hi,
I know it's hard to diagnose noises but just wondering what are some things I can check.

It doesn't happen all the time. It's when the rear wheels hit the bump, sometimes I get a 'clank' sound (between a clank and a clunk).

I know it has to be in the rear somewhere because it doesn't make the sound when the front wheels hit the bump.

thomas

<{POST_SNAPBACK}>

Loose spare tire? Had more than one of those.

tlocus · May 1, 2005

Thanks for the replies.

I'll recheck the spare tire, although I recently cranked it up tight.

It also happens when just coasting (not under power).

Rear shocks are new and also checked all lug nuts.

t

Halen5150 · May 2, 2005

Maybe the leaf springs are rattling? Mine on my '00 were very noisy until I had some bushings added to quiet them down.

tmf6902 · May 2, 2005

Halen is onto something. In the front and the back of the leaf spring there is a rubber bushing. When the spring contracts without that bushing, it makes a clank noise. Mine apparently fell off, dealer replaced it under warrenty.

tlocus · May 2, 2005

Just checked out the leaf springs.

Just to be sure...the bushings are round and flat (about 2.5"DIA and 1/8" thick) and mounted on each end of bottom leaf? If so, it seems like all bushings are there.

I did notice on drivers side the ends of the very bottom leaf(short leaf) have about a 1/4" to 3/8" gap from the next leaf up.

The passenger side is about 1/16" to 1/8" gap.

Could it be possible that this drivers side bottom leaf be 'clapping' with the next leaf up even with the bushings?

t

tlocus · May 4, 2005

Well, Yesterday I brought it to the dealer to look at.

They pretty much checked everything, made sure all U bolts etc... were tight and lubed it up. Still does it, they don't know where it's coming from.

They did say the U joints had a little play in them, but not much(probably not enough to make the clank).

Is there a rod inside the rear differential tube that connects to the rear hubs? Just wondering if something inside the diff. tubes might be moving around?

t

GM-Tech · May 4, 2005

Is there a rod inside the rear differential tube that connects to the rear hubs? Just wondering if something inside the diff. tubes might be moving around?

Not a chance.

05_2500HD · May 9, 2005

Maybe the leaf springs are rattling? Mine on my '00 were very noisy until I had some bushings added to quiet them down.

<{POST_SNAPBACK}>

He's right, my 2000 made the same exact noise...there were insulators that the dealer put on (they were rectangular with a slot on one end and fit on the ends of the "free" leaf spring)

Once it was done nice and quiet

tlocus · May 9, 2005

05_2500HD, so before you had them put on the rectangular ones, did you have the round thin ones?

Are the rectangular ones a lot thicker? (my OEM round ones are about 1/8" thick)

t

Halen5150 · May 10, 2005

The ones they added to my leafs are round also, and they're quiet as can be. Could it maybe be a loose exhaust hanger or something? Maybe one of the welds broke loose? That's probably a shot in the dark, but I don't know what else it could be...

05_2500HD · May 10, 2005

05_2500HD, so before you had them put on the rectangular ones, did you have the round thin ones?

Are the rectangular ones a lot thicker? (my OEM round ones are about 1/8" thick)

t

<{POST_SNAPBACK}>

Yes I had the small round ones, if they sit right on top of the leaf then yes. Those are original. The ones that the dealer put on were rectangular in shape, roughly 1/2" thick and had a slot so they fit completely over the end of the leaf. They were maybe 3"x2" square. They also put on round "donuts" (kind of like what some imports use as exhaust hangers). Those were slipped over the "free leaf" and slid all the way towards the center of the leaf pack until they were snug. Total used were 2 rectangular insulators and 2 round donuts per side. I took it to 3 dealers before one knew of a service bulletin regarding this. Trust me this is the noise and I searched for it for months before it was solved.