Chasing a Clunk after Roll-out

AlBackus36 · 09:18 AM

OK,

I thought making a thread about this may be helpful as I'm stumped and now reaching out to random people to get ideas on help. I'll add a video to share tonight when I get access to the right computer.

Car is an '87 G50 car with a 3.6 swap. Rebel racing rear bushings, rear monoballs, tarrett sway bar mounts with rubber bushings and Elephant adjust end links attached to the spring plates. There is very little clearance (0.10") between the sway bar and the trans (I have 1" spacers already installed). Everything on the car is new. There is likely 3k miles on the suspension parts total.

When I roll-out from a stop, there is a delayed clunk. The clunk severity depends on how hard the roll-out is. It's a single clunk that isn't repeated until you stop and start again. There is no clunk from slamming on the brakes. It doesn't clunk over bumps. Only on roll-out (that I can hear/tell). You can feel the clunk in the body and if I was to guess where it's coming from it's beneath my seat, in the trans tunnel area near the diff/trailing arm attachment. It's not coming from the front of the car and can't be felt in the steering wheel. EDIT: Car is pretty low with a rear fender height of 24 1/8"

I have checked:

1) Rear shocks torque and grabbing them trying to move them
2) Driveline lash
3) Torque of every bolt you could think of
4) Looseness of anything with weight, ie muffler, oil tank, etc.
5) Jacking a wheel and trying to move it whichever direction

Has the audience seen a G50 car with a rear sway bar slapping the trans from small clearance? I had the wife jump on back of car while I watched and I saw very little deflection or reduction of the gap between the bar and the trans so maybe that's not it. I thought about taking a dremel to the bar (solid I believe) to try and get another 0.050" clearance and see if it quieted down. Would prefer not to grind on it. Likewise, I could try removing the bar completely and see it stops.

Any other ideas about clunk noises in rear? Would an LSD make this clunk? I notice the noise at maybe 1-3mph so I figure if I'm moving it can't be driveline lash related.

I'm completely stumped and will take any suggestions. Stupid noises like this take enjoyment out of the experience. Color me motivated to fix it.

Thanks for reading!

AlBackus36 · 02:51 PM

Delete.

AlBackus36 · 08-22-2025, 02:48 PM

0:02 mark is the sound or 2nd clunk you hear in video. I heard it once much louder than this but was unable to recreate it on video. A picture of the rear sway bar and its clearance also included. Not super great but I don't see signs of collision.

My take away from my latest drive is that it occurs when the trans/engine is warm. It's intermittent and feels (like thump) like it's coming from behind/under me. Do the Heim joint sway bar end-links knock/thump?

Sometimes I think it's someone (me) lost a 10mm socket somewhere...

Gonna just keep driving this thing till something pops out.

trials935 · 06:11 PM

See if you can eliminate brakes/ pads shifting/ sticking in the calipers by coming to a stop using only the handbrake, not the brake pedal and taking off again to try and make the clunk happen. Also, you can put a piece of thick rubber between the sway bar and Trans to temporarily eliminate that. If necessary, I would dremel a bit off the aluminum Trans rib rather than any off the sway bar, which will just create a weak spot on the bar and might fracture there in the future. Are you positive that the 2 large bolts that attach the trailing arms to the torque tube are very tight and the mono balls are not shifting in the mounting tabs.

A930Rocket · 06:10 PM

I was going to say, remove the sway bar and take it for a quick spin. That will eliminate one variable quickly. As you start to remove it, you may see rubbing marks on both of them if they are making contact.

How old and what type of motor and transmission mounts do you have… rubber, urethane, solid, etc? Your engine and transmission may be shifting, just enough to make contact with the sway bar.

Kevin Stewart · 08-22-2025, 09:17 PM

I would relook at the bushings you just put in, I have had them snap and pop.

AlBackus36 · 08-23-2025, 03:42 AM

Thanks you guys. Few more things to try here.

Trials, will do. That's a good idea with the e-brake. Good put on grinding the rib rather than the bar too. I know the trailing arms are torqued to 90ft-lbs and that the monoballs were new when installed 3k mi ago. I don't know if things are shifting and have suspected that. Unfortunately, it's a major ***** to take the arms down and likely won't check the balls themselves until next eng drop.

Rocket, yes agree. I'll pull the bar and just eliminate it completely. I'll need to let the end links dangle as they double as spring plate eccentrics now, but shouldn't take more than 15 min.

Kevin, you've had the phenolic bushings snap on you? I do have a little concern that there is something like 1mm gap for the bushings. That means they can point loaded against the CRES bushings on the spring plates, but also means there is room for movement. Others I've asked with the same kit have said they don't hear noise from them, but I could see this kit slapping

JW's swapmeet today, then tomorrow I'll experiment some more.

Thanks a bunch again guys!

Kevin Stewart · 08-23-2025, 08:45 AM

Mono balls are kinda weird they dont have the same travel as some ball joints/heims. I have also had them bind.

I would take off the wheels, shocks and put the suspension through travel, I bet you find it.

AlBackus36 · 08-24-2025, 02:16 PM

Good exercise. Found a witness mark on the sway bar when taking things apart and some more marks on the RH shock. The hard oil line that crosses under the motor needed adjusting to clear the shock. This explains why I thought the RH shock was loose. I ground on the trans rib some, but I'm continuing to get a noise. I think I had two or more issues at once that made it seem like it was coming from multiple places. The shock ride seems fixed, but I think the sway bar is still hitting. I didn't run with no sway bar yet as I thought the shock was the real cuplrit. I'll shim the bar more next or try running no bar. Either way I think it still needs a bigger gap.