Thunk In the rear

Ok, so there has been a thunk coming from the back of my truck and it seems to be getting louder.

Just to preface, I haven't brought this to the dealer yet because each time I bring in the truck I seem to get resistance due to the mods I've done.

My Truck: 2020 OR with Icon 3aal and ADS shocks = 2-inch lift.

The Symptom: When driving over potholes or bumpy roads there seems to be a thunk coming from the back passenger side of my truck. Honestly, it sounds like something big is loose. This sound does not appear from simply flexing the suspension, such as driving over something, but instead from rapid movement of the rear. Moving the truck side to side doesn't make the sound come out, but if I jump up and down on the bumper the sound is very much apparent as if someone is banging on it.

What I've done so far: Re-torqued U-bolts to 120ftlb (per-Icon). Checked leaf bolts torque. Tightened bed bolts. Tightened spare tire. Generally grabbing of things to see if they're loose.

I've attached two videos of me jumping up on down on the bumper, please ignore the leaf springs squeaking.

This is the truck on the ground:


This one is only the rear passenger tire on a ramp. It almost seems like the sound moved from the passenger side to the driver:


Picture, figured I'd throw it in.

Thanks for the help everyone, I'm genuinely stumped

 

I think you need a helper to jounce the rear while you are underneath.

A good place to start is whatever was touched last. Continue to go over all the hardware on the suspension. Shock bolts, spring hangers, like you have been doing

 

I had a thunk in my front. After checking everything over and over multiple times I found that my shock reservoir was never pressurized at the factory and the floating piston inside was knocking against the inside of the resi. After pressurizing the resi with nitrogen it has been good.

Assuming you have checked everything else, you could check the pressure in your shock resi if you have a high pressure gauge. The fronts on kings are usually set around 125psi. No idea what the rear of an ads shock would be.

 

I had a buddy do this for a quick second already but nothing seemed to be obvious. Guess I'll have to do it more throughly.

This was what I'm thinking/worried it might be. I don't have a high pressure gauge nor do I know what the psi level should be, I'll check in with ads and see what they say. Would any old garage be able to check or do you think I have to track down a performance suspension shop?

 

A bike shop will have a high pressure gauge. If it’s low you’ll have to find a shop that can pressurize it with nitrogen. You could always check both sides to see what the other side is set at. Checking the pressure with the correct pump/gauge should only drop it a couple of psi.

 

Thanks. I'll track down a shop and let you know how it turns out.

 

Before you go that far try removing the shock and see if the noise is still there. That’s a easy troubleshooting step that will either isolate the problem or save you a bunch of running around.

 

maybe if you had someone jump on it while you were under it to investigate you would get somewhere with the clunking noise.

 

Thanks for the help everyone. I ended up removing the shocks and the sound went away. However, when I inspected them they appeared to be in good working order.

So I reinstalled and poof, the sound went away. Gonna cough it up to poor initial installation.

 

Missed opportunity to title this “Thunk in the trunk”.

Glad it worked out after reinstalling, and nice to see a thread that was updated with the fix.