New to forum posting, but need some insight from the gurus out there.

I have a jk with 4.5" mid arm lift with non adjustable arms. I recently had pretty bad wobble which found to be the drag link lower ball joint gone bad so i took her off the road to fix and while doing so i decided to put a 1.5" block in the back to tighten my springs seeing how the previous owner put 2" cup in front to make it bulldog.
Well i installed with no problem and now when i drive down the road and slow to a stop on or off the brakes i get this weird thumping noise- thumps slow down as creeping to a stop.
I do not have anything stuck in my tires, i have gone over every thing i think could of mimic that noise. I looked at the drive shaft and the angle looks completley fine to me, but im no expert.
I have not opened the diff yet or pulled my rotors off to look at axles. i checked my tires to make sure the lugs were tight to 100ft lbs. I jacked the rearend up and had someone drive it and coast it to a stop and could not replicate the noise on jacks- only does it when going down the road.
Im stumped that it happened right after putting those lift blocks in the rear.
I decided to take them back out to see if it would fix it and it is still doing it, but kind of quieted up some. Could it be that the angle screwed something up with the driveshaft or what??

 

I don't understand the 1.5" block to "tighten up" your springs. Are saying you added a spacer on top of your springs? Not sure how that would tighten up your springs.

Did you make sure your springs are indexed correctly? Maybe they twisted on you. Did you try jumping up and down on the rear bumper?

 

Yes I added the spacer on top to help level the jeep out. We made sure the springs were turned right and yes we have jumped on it and drove it around the property bouncing around. I put the springs exactly how they were before and after installing/removing the 1.5" lift. I don't understand the thumping in the rear end only when slowing down. Nothing at acceleration or during driving.

 

What about when you put it in reverse and gas it? That would mimic the deceleration force I would think. Sounds like it could be a CA bushing maybe? What kind of arms?

 

I can get the same noise in reverse with enough speed but only once rolling to a stop. And does not matter if clutch is depressed versus neutral.

As far as I can tell the arms are oem. They were on it when I bought it. Their square and non adjustable. I plan to replace them with rock Krawler adjustables after I work this issue out.

 

Is it a rotational thumping?

 

Yes it is but close together thumping almost clacking.

 

I had the same issue with my Jeep and it ended up being a loose control arm. I put 4 jackstands under the axles and took the tires off, this allowed easy access to every joint while keeping the suspension in a neutral position. I then loosened every arm and jumped on the bumpers to prevent any type of binding. Finished with a triple torque of all the bolts and put the tires back on. No more thumping.

 

I'll try that and report. Thanks

 

Pulled the diff cover to find the ring gear missing multiple teeth. Guessing that was the source of my knock.