Strange Noise When Stopping Backing Up

[Fifty150hs]

I have a 2006 with 3.0. I have a weird clunk I get when coming to a stop while backing up. I have replaced the trans/transfer mounting bushing. The center driveshaft support is new. The front guibo is relatively new. I recently replaced the differential mount bushings. I have one relatively new rear half shaft. The other is was replaced awhile ago. I replaced the rear subframe bushings about 10,000 miles ago. All of the suspension bushings, links ball joints were replaced about 84,000 miles ago. New adjustable control arms were installed about 17,000 miles ago. I also put coil overs all around on it about 17,000 miles ago and lowered it 2", hence the need for the adjustable control arms.

When coming to a stop while backing up there is a distinct clunk in the rear when I apply the brakes. I haven't been able to pin down what it's coming from and as noted above just about everything has been recently replaced. The older bushings look to be in good shape.

Any ideas?

[Henrym3]

Excessive play in rear diff. Loose calliper mounting bolts


Sent from my iPad using Xoutpost.com

[Fifty150hs]

Originally Posted by Henrym3

Excessive play in rear diff. Loose calliper mounting bolts


Sent from my iPad using Xoutpost.com

I'll check the mounting bolts, but wouldn't that make a sound in both directions? What's the best way to check for excessive play in the rear diff?

[Henrym3]

Checking the diff without taking the cover off is difficult as any of the gears in there can cause a clunk. Get it up on axle stands get the wheels well off the ground and see if you can replicate the noise by going from forward to reverse and braking. Get someone to drive or watch and listen for the noise or possibly see some movement on another component. Diffs rarely seem to go wrong but if you can’t find the noise it’s worth trying. You have checked the oil level. It may even point you in some other direction. Be careful,be safe if you haven’t got the equipment to get it off the ground don’t bodge or get underneath.
As for the callipers as you drive forward and brake it tends to keep the callipers at the top end of the bolts if you understand what I’m saying and if you reverse it tends to move it down because you braked. On selecting forward gear the movement is less severe so less noise. Best way I can explain.


Sent from my iPad using Xoutpost.com

[Fifty150hs]

Originally Posted by Henrym3

Checking the diff without taking the cover off is difficult as any of the gears in there can cause a clunk. Get it up on axle stands get the wheels well off the ground and see if you can replicate the noise by going from forward to reverse and braking. Get someone to drive or watch and listen for the noise or possibly see some movement on another component. Diffs rarely seem to go wrong but if you can’t find the noise it’s worth trying. You have checked the oil level. It may even point you in some other direction. Be careful,be safe if you haven’t got the equipment to get it off the ground don’t bodge or get underneath.
As for the callipers as you drive forward and brake it tends to keep the callipers at the top end of the bolts if you understand what I’m saying and if you reverse it tends to move it down because you braked. On selecting forward gear the movement is less severe so less noise. Best way I can explain.


Sent from my iPad using Xoutpost.com

Makes sense. I'll get her up on stands this weekend and see if I can replicate the noise. I'll also double check the caliper bolts. Thanks for the input!

[andrewwynn]

The prime suspect is either something loose in the braking like mentioned or usually it's a ball joint or similar.

Are there any joints you didn't replace and regardless, double check; if you have air springs let out the air so you can manhandle. Any tire wear?

[80stech]

@andrewwynn was it you that had an extension tool made up to bolt to the wheel hub and check for loose front end parts?

[Fifty150hs]

Found it! It turned out that a while ago when I went over a speed hump too fast and bottomed out part of the rear subframe. It was one of the "wings" that the swing arm bolts to. Part of it was bent toward the swing arm, almost touching. There's enough flex in the swing arm bushing when braking in reverse it moves and hit the bent mount. So I went after with a BFH and a pry bar and bent it back away from the swing arm. No more noise.

[andrewwynn]

Originally Posted by 80stech

@andrewwynn was it you that had an extension tool made up to bolt to the wheel hub and check for loose front end parts?

I linked to that product but never had one. It's impossible to test for loose ball joints when 12-1800# loaded on them by hand. You can usually move it with a crowbar though. With pressure off I could move mine 2mm with a couple fingers! (Chewed though my tires to the "redneck wear bars" (steel belts) in under two weeks!

[andrewwynn]

That's great you found it!


Sent from my iPhone using Tapatalk Pro