Clunk on Acceleration

[Bad Larry]

I recently purchased an 06’ LJ and have been absolutely loving it. With that being said, when accelerating from a stop, there is a distinct “Clunk” coming from what sounds like the rear driver side. It only happens when accelerating from a complete or near stop, and not from a roll. I’ve attached a video of what it sounds like and I’d appreciate any pointers as to what to look at first.


View: https://vimeo.com/1183217599

The front and rear U-Joints are brand new along with all control arms. 2.5” RC coil lift.

 

[LJBean]

I've had shock extender brackets on the lower rear shock mounts come loose and have a similar effect.

 

[Bad Larry]

I've had shock extender brackets on the lower rear shock mounts come loose and have a similar effect.

I have factory shock mounts

 

[LJBean]

Have you tried pulling your rear DS to see if it still happens in 4WD? If that makes it go away, it's likely related to a DS joint.

 

[GATORB8]

I’d get under and pull and shake on everything. Could be a backed off nut.

 

[macleanflood]

My control arm bushings were shot. 20 year old rubber...

-Mac

 

[Bad Larry]

Wanted to update this and hopefully get some more advice.

So far I have:
- Replaced the rear driveshaft
- Loosened and retorqued all suspension components
- Replaced the transmission mount
- Replaced shocks

At this point, I’m running out of ideas. It only happens when accelerating from a full or near stop. It’s usually just one snap/clunk then it goes away until I stop again. I have no vibrations or noises at speed. I’m going to check on the brake backing plate bolts and differential next.

When I was replacing the old driveshaft, I pulled the rear and drove in 4HI and could not get the noise to replicate. Came back when I put the new driveshaft in.

 

[tm dean]

Third member/ pinon excessive play?

 

[Bad Larry]

Third member/ pinon excessive play?

I don’t think so. Felt within normal limits to me. The noise often occurs 1-3 seconds after the wheels have already started turning.

 

[GregBelleville]

Maybe opening up the rear diff makes sense to do next to see how everything looks.

 

[WVJeep304]

I had something similar going on for a month and couldn't track it down. I eventually discovered something I was hauling in the back would roll into the fender well or tailgate as I accelerated. This sound reminds me of that and makes me wonder if it's something under the jeep that is making contact when you move forward, as opposed to something rotating. Maybe something came loose and is either swinging around or able to rock back against something once you begin to move.

I assume you've ruled out anything on the interior at this point and narrowed it down to the outside & under the jeep. It's just hard for me to tell listening through my phone exactly where it could be coming from, as well as what the contact sounds like.

 

[tr21triton]

I'm with MAC, control arm bushing allowing the diff to flex. If they're original they need to be replaced anyway. Just replaced them on my brothers '06 96k mile one and it made all the difference in handling. I don't know how many miles you have on yours, i think it cost us under $300 to replace all 8 control arms and the front and rear track bar bushings. It wasn't very hard and took us a little over a day to do.

 

[Bad Larry]

I'm with MAC, control arm bushing allowing the diff to flex. If they're original they need to be replaced anyway. Just replaced them on my brothers '06 96k mile one and it made all the difference in handling. I don't know how many miles you have on yours, i think it cost us under $300 to replace all 8 control arms and the front and rear track bar bushings. It wasn't very hard and took us a little over a day to do.

Dealer replaced all of the control arms with SKP parts. They don’t have more than 5000 miles on them.

 

[inkedrose]

My control arm bushings were shot. 20 year old rubber...

-Mac

I had same problem

 

[GoldenGorilla]

I was making some fine adjustments to rear driveshaft angle on mine and thought I had everything snugged back up. Not quite perfect on the rear drivers frame side lower control mount and it was clunking just as you describe. A half turn or so and it was sorted.

 

[Camdenst]

Transmission mount? I have a very similar clunck only at take off.

 

[Bad Larry]

Transmission mount? I have a very similar clunck only at take off.

Swapped it last week.

 

[Bad Larry]

Did some more poking around and noticed I had some wear on my rear track bar. Not much clearance between the exhaust pipe. Definitely think this could be the winner, going to try pulling the pipe to verify.

 

[jonny jeep]

I had a clunk years ago from setting off in first, but also on the change to second. The joint between the cat and back box had come loose (clamp may have corroded, I forget) and the rear section of exhaust was obviously swinging back the clunking as it came forward to hit the cat.

 

[WestCoastDan]

Similar noise was mostly solved with a new transmission mount in our '03.
Motor mounts are next.