Can anyone identify this noise?

Hey TW.

I've been trying to chase down a knocking or popping noise that sounds like it is coming from the drivers side leaf pack. The truck has about a 2.5" lift in the back with Icon RTX springs at level 2. Shocks are Dobinbson extended travel. All of the components are low miles and were in good shape when I had the springs off about 3 months ago to install my Hammer Hangers. I have been under the truck extensively shaking and pulling on things but I can't reproduce the noise when the truck is sitting still. Here is what I think I know.

Only happens with low speed bumps
Worse in cold weather
The noise correlates to sharp compression or extension of the drivers side leaf pack.
It's not the hitch or spare tire.


Again, I have been under the truck quite a bit looking for a smoking gun and have come up empty. The bungees in the video were a test of another theory that didn't pan out LOL.

https://youtu.be/N505i40HwiY

Thanks in advance

 

Is the bed loose? The right front bed bolt right behind the cab is known to loosen up and allow the bed to rattle up and down

Go to each corner of the bed and lift up. If it's loose you'll feel it

 

I checked the bed this morning. I shook the hell out of it and can't get any movement or noise.

 

I think that I may have found it. I inspected the lower shock mount on the driver side and found this. I remember thinking that there should be more clearance when I installed them about a year ago. Bushings are good and the shocks didn't move in the mounts at all. Has anyone else run into this with these shocks?

 

That's a good find and if it's your culprit would be the easiest fix. I'd take a grinder disc to where it hits the mount on the axle and give it a little extra clearance, then a little spray paint and you should be golden.

I noticed similar clearance issues when installing my lift which consisted of Deaver U402 stage 2 leaf pack + Fox 2.5 Performance resi shocks which is similar to yours in height and components. The lower rod ends they put on these things are so freakin oversized compared to some others I've seen. I get why but boy do they use every millimeter of clearance (and sometimes a little extra). Mine don't make noise and I think they have "self clearanced", but if mine did make noise from that same contact point I'd do the same thing and massage it a little with the grinder.

 

I also had to grind down my rear shock mount slightly in that area for clearance with my Dobinson's on my left rear side.

 

Thanks for the replies

I think the fact that I am running 2.5 degree angle shims could be the difference between clearing and not clearing with the Dobinsons. I think it makes the driver side worse and the passenger side better due to the reversed orientation of the shocks. I haven't pulled it yet but I remember the passenger side not being as close.

I'm grinding the shock instead of the mount as it is less permanent. Hopefully the noise goes away. Even if it doesn't I'm glad I addressed it.

 

I notched out both sides even though there had only been contact on the one.

 

Well, it turns out it wasn't the shock clearance. I replaced the isolator pads on the leaf springs this weekend and replaced the stock rubber bushings with the energy suspension kit. I even switched the leaf packs to the opposite sides of the truck. So far nothing that I've done has changed the noise at all. We had a rare 70 degree day last week and the noise almost completely went away. Here is another video from a different angle on a relatively cold morning. You'll here the noise clearly when I go over the man hole covers. Gonna keep looking.


https://youtu.be/994YBJ0b4Cg

 

I think that I finally figured this out.

I pulled the rear shocks this weekend and when I reinstalled them I put the thickest combination of 12mm shims that would fit between the bushing sleeve and the lower mount. Noise is totally gone.

The theory is that the clamping force on the sleeve wasn't enough to keep it from shifting over sharp bumps when the shock oil is cold and the damping force is higher than on warm days. I think that it held tight enough that I couldn't recreate the noise when the truck was standing still.

I ended up putting .7mm of shims on each shock and it has been completely silent even though the weather has been cold. Seriously glad that it's fixed. Here is a link to the shims.


https://www.mcmaster.com/98089A344/

Hopes this helps someone else.