Rear Axle Clunk

Hey yall. Need some help finding out what this clunking noise is. Sounds like it’s coming from the rear axle. I recently installed ICON 2.5” piggyback shocks in the rear, and since then I’ve had this noise only over bumps. Otherwise, the truck drives perfectly fine. No vibrations or noises unless hitting bumps.

I’ve re-torqued my u bolts to 90ft/lb, made sure the shock mounts were tight, and replaced all my u joints and carrier bearing, as well as greased my slip yoke. Still makes the noise. Should I grab new u bolts? I did have to remove them and re install them to get shocks in. The leafs aren’t broken, and the shackles shouldn’t be loose. I’m kinda lost here.

Heres a video: https://drive.google.com/file/d/1DjrErt0xM1hdOISaakl9k0mx2259WWRl/view?usp=sharing

 

How much lift do you have on the rear? Sounds like the shocks might be at full extension, especially since you had to remove the u-bolts to get them on.

 

It's about a 3" lift, nothing crazy. That was only going over a small bump. It makes the noise when going over any bumps at all.

 

What size lift block do you have on the rear? The one supplied with the Icon Stage 3 system? Which is 1"?

 

I don't have a lift block. It's all the same except the shocks. I did have to remove my u bolts to install the shocks, but I just put it all back together as it was.

 

why the need to remove the U bolts?

As for the bump noise…are the upper rubber shock isolators located (as in stacked) in the correct order? Can you take any pics of it?

 

This is where I'm questioning. So, you couldn't compress the Icon shocks to get them to go into the mounts on the axle? I've never not been able to compress a shock enough either by hand or with a pry bar to get it to mount.

 

No I wasnt. But to be fair, theyre really thick. Like twice as beefy as my 5100's. I would imagine thats how you're usually supposed to install them. They ride perfectly fine otherwise.

 

I had to remove my u bolts to allow enough leaf spring droop to install them fully decompressed

 

We might need more than a 2 second video, maybe even from under the truck if possible. Photos might help too. There are some pretty keen eyes on this forum.

 

“fully decompressed”…as in full extension? Can you post up pics?

 

You 100% positive it’s coming from back?

What did you do (and when?) to the front to lift it? What did you do to compensate up front for the added stress on swaybar links? Did you spin them back so the bushings weren’t hammered? They’re notorious for clunking if you don’t use extended links or at least adjust the links down so the bushing is barely engaged after you lift.

And are you sure the rears are adjusted properly, specifically the top bushings aren’t overcompressed? They need to be barely engaged when you install, and over tightening them down would totally cause clunking as well, and premature failure.

Also, what did you do to fix your braking with regard to the LSPV? Did you use LSPV bracket to relocate, readjust the LSPV, or nothing at all?

What I’m getting at here is: There is more to updating your rear to lift stuff (and read shocks don’t really lift) than unbolt shock, put in shock, call it a day.

It’d be helpful to know EVERYTHING you’ve done and when, we really want to help you but kinda need your life story here. I don’t think we’re hearing it all.

 

yes its definitely from the back. the front also has ICON 2.5" coilovers, but is not having any issues at all. Prior to that, I had 5100's all around. I did spin the links back. When the front of the truck goes over a bump, it sounds fine. When the rear goes over, it clunks.

The rears should not be overcompressed, they were loose when installing. I only tightened the after everything was back together.

no other supporting mods in the rear, but the shocks never mentioned the need for any. I had 5100's in the rear prior to this with no issues or noises. The icons dont seem to lift it anymore than the bilsteins did. Theres no unnecessary tension on any lines in the rear either. Same with the front. I made sure to double check the u bolts were torqued back in correctly as well.

Here's a link to the rears I have:
https://iconvehicledynamics.com/acc...ra-0-3-lift-rear-25-vs-piggyback-shocks-pair/

 

Yes. They are really beefy and impossible to install by compressing them by hand or whatever. Me and others on youtube install them by separating the axle from the frame as much as possible to install at full extension. You gotta uninstall and reinstall the u bolts for that.