Another rear thumping noise

I did a bunch of searches and checked a few items to no avail.

Here it is: A 2000 sport, 8.25" w/ '98 zj discs (salvage), 2" OME springs @ med rate. New TW driveshaft, edelbrock extreme non - res shocks, JKS BPE.

Ever since I did the new springs the truck developed a thump in the rear and it *sounds* like it's in the center.

Here's what I checked:

fuel tank is snug

shackle bolts don't appear to be striking the rail, I did install them with threads inboard

The upper shackle bushings are origional. I wonder if age/corrosion in this area could create a thump.

BPE's are snug, they were loctited in

I adjusted the gate snubbers out a bit, so if it's the tailgate I wouldn't know what else to do. The hinge pins are just a hair sloppy. Gas supports have been dead for years. Vise grips.

Noise happens on speedbumps. Sudden shockload stuff. A nasty dip soaks up really nice. I can feel the rear suspension cycle through all nice and controlled. I did have the swaybar ends mashing some inner fender metal, but I've "clearanced" those spots and put nail polish on it to see if it's still hitting there. no contact there any more.

I had one of my front control arms come loose and could of swore the pop/thud was coming from the back. It would only do it on speed bumps and driveways.
Best way to find a popping/thud noise, is to have someone sit in the back and/or stand outside and listen for it.

Gas supports have been dead for years. Vise grips.

Click to expand...

You can buy these at any auto parts store. You'll be amazed at how nice it is to just pop the hatch and have it lift by itself and stay up. No more vise grips.

I'll wager $1.37 that you've got a bad shock out back.

Maybe your shocks are too short... I just had that happen to me after adding 1.5 in. shackles to a 3 in. lift.

checked the ubolts on the axle for the springs?

Transmission or engine motor mount broken?

Thanks guys, I checked it out and all seems ok suspension wise. The sound is definately coming from inside the tank. I found a way to reproduce the noise in the shop.

I'm pulling the tank out asap.

I smacked a tree in a campground in reverse hard enough to dent the bumper and DS bracket in about an inch. I think something let go in the tank.

Well, how's THIS for bizarre!?!?!

The noise was being created by a fuel pump loose in the tank. Not THE fuel pump, but another separate fuel pump connected to absolutely nothing!

All I can figure is... well... I can't think of a single reasonable explanation for this. Did a previous owner stash a spare? Did a hack mechanic drop the old one in there when replacing it? Who knows. I'm onto the next problem. I suspect I hit the 0331 lotttery.

I could shoot myself in the head for buying this thing.