Diagnostic assistance request: rear suspension clunk

[MRGTX]

So I've replaced the whole rear end of the car on my own at this point. There aren't a lot of mysteries or variables going on back there which is why this is a bit perplexing.

So most often I'll hear this clunk when reversing and hitting the brakes to stop. It seems to emanate from the rear of the car, seemingly from the right rear though it's hard to tell. It also happens once in a while when I'm slowing to take a 90* turn, as the transmission downshifts. I suppose that it seems to be related to changing the direction of force on the drivetrain, not induced by hitting a bump.

It started after replacing 1.5" lowering blocks with 1" lowering blocks. It seems pretty consistent (not getting worse) after a few hundred miles...but something isn't right. I climbed under the car and checked all of the U-bolts. Everything seems tight.

The list of potentially relevant components:
A904 with a TF2 shift kit
Hotchkis leaf springs
Fox shocks (as prescribed by Hotchkis)
8 3/4" rear (Moser housing)
Eaton Trutrac helical differential
A recently installed pinion snubber...which is admittedly pretty close to the body when at rest, part of what prompted me to find another 1/2" of suspension travel.

Could this be related to the internals of the TruTrac? Could the axle be twisting enough to cause the snubber to knock against the floor? Does it even move that much? The noise seems maybe a bit harsher than what I would expect from the rubber snubber...and I don't hear when I hit bumps.

Any suggestions of what else to check would be welcome.

 

[MRGTX]

Here’s a pic of the current ride height. I took this yesterday...

 

[mderoy340]

Take the snubber off and see if the clunk goes away. I drop my snubber for street driving and raise at the track. Fuel load also changes how close the snubber rides.

 

[Oldmanmopar]

This may not be your problem but its a start to check. Was your car originally equiped with a 7 1/4 rear . If so the housing bump stops are shorter for a 8 1/4 and a 8 3/4.

Are your leaf spring shackles angled back to far from the flatter leafs. This causes the spring shackle to hit the bracket support. They make a Z style shackle to eliminate this issue. If they are against the bracket they will knock on accelaration and deccelaration with spring wrap. I have notched the support in the past. It will be the inner shackle bar hitting.

You checked the diff and drive shaft slop so you can eliminate that.

The correct Diameter bolt in the front eye. Early cars pre-72 have a smaller 1/2" diameter. 73 and later have a 9/16 bolt. Using the earlier spring eye with the later spring mount could be another problem.

Make sure your axle bearing adjustment is correct if using tapered bearings

If you are using the green bearing style the removal of the axle adjustment separator is required. or you must have the axles cut if using a unit that is not removable such as the alburn/cone style unless disassembled.

Check your rear bushings. some of the poly bushing don't last long at all.

Again these are just some things to check that I have run into over the years that create problems. I do not know your car so they might not pertain to your issues.

There may be members such as "Yellow fish with no teeth just lips" that will find issues with something I am saying. He always does. Don't mind him. He has problems with everything myself and some other members say. He is just here to cause conflicts with those he don't like because he don't like being reminded of how little he knows . Or he is just jealous that he only has Tonka's to play with.

Good luck, Steve

 

[kgip2k]

Did you change or shorten the driveshaft? Pretty sure the 8-3/4 takes a little shorter driveshaft.