Rear clunking!!

[iamsam]

Updated, i replaced CV shafts, still clunking!

UPDATED again, 2010-08-09, replaced diff, STILL clunking!!!!!!!!

UPDATED again, 2010-12-07, tightened trailing arm bolts, NO MORE CLUNKING!!!!

This may concern the subframe OR the drive system, so i put this thread in General Tech.

Backstory:
JUST replaced ALL rear bushings w/ polyurethane, and ALL new brakes. BEFORE the subframe overhaul there was a louder clunking from the rear which was stimulated by driving over bumps, and it seems the new bushings fixed that, but now AFTER everything is back together (and working amazingly, btw), there is another clunking, which may have been there before, but I am not sure.

Symptoms:
A clunking from the rear of the car when quickly applying and releasing torque to the drivetrain, i.e. tapping the gas on and off, loading and unloading the drivetrain very quickly. I can do it while stopped in gear and releasing the clutch fast, or while moving by stomping the gas pedal.

Possible diagnosis:
COULD be CV joints, one of them has a BAD rip in the outer boot, but when jacking up the car and turning the wheel, there doesn't seem to be inordinate play.
COULD also be the diff, when parked, w/ ebrake applied, and in gear while engaging and disengaging the clutch quickly, the sound is hard to pinpoint, (while lying down behind the car), but it SEEMS to be coming more from the diff than any of the CV shafts.

So, can i tap into the vast knowledge base (and ass-hattery) that is R3V? ;)

Thanks guys!!

[Dermeister3]

Shock mounts, if it sounds when you hit a small bump too. if not, no idea

ive had them go on every E30 ive ever owned.

[iamsam]

Shock mounts, if it sounds when you hit a small bump too. if not, no idea

ive had them go on every E30 ive ever owned.

shock mounts are new IE billet aluminum, and its not those. It happens when i load/unload the drivetrain, not at all with suspension movement.

[e30rapidic]

sounds like guibo or most likely the centre support bearing.....

[llll1l1ll]

Mine is clunky, too.

I reckon it's the driveshaft moving back and forth, as well as having play in the u-joint (or whatever kind of joint) it is in the middle.

Unless it doesn't have one.

Also, check your diff fluid.

Maybe the diff just has some extra play?

[iamsam]

BRAND new guibo that i installed after doing bushings, so it can't be that, and i took the entire driveshaft out and re-installed it, and inspected the center support bearing and it seemed fine, as in the driveshaft seemed to be held well, while there was no rips or cracks in the rubber. I did notice some play within the diff when i jacked up one wheel and turned it back and forth while the car was in gear....

[iamsam]

and also, i am buying brand new CV shafts tomorrow from Napa for $64 a piece (some local car club discount), because i need them anyway because my CV boots are crap. So that should eliminate that as a problem so the diagnosis can become more focused....

[dashboardmonkey]

make sure your diff mounting bolts are tight

when i did the motor swap in my 86 i swapped out the diff too and forgot to torque down the diff bolts

sounded like what you are describing

[iamsam]

hmmm..... i did tighten them pretty good when the subframe was on the ground.... I will give them another yank and see if they are loose....

[Atreus]

i find it rather ironic how our cars have the same problem, you're just fixing yours ahead of mine.

the subframe, your suspension, the CLUNKING! etc. i need to do the same to mine, lol.

[khalild]

if its the driveshaft it will do it whenever u shift gears or shift the trans(if u have an auto)

[iamsam]

it happens when i get on throttle and off throttle quickly, not necessarily when I shift gears, although, WHILE shifting, I get off throttle/on throttle. But I can replicate the clunk without needing to shift gears.

And Atreus, by the time I am done with this, I will be able to answer any questions you may have! ;)

[iamsam]

Update

So i installed brand new CV shafts!!!

And here is the conclusion: The clunk is still there with the on/off torque to the drivetrain, but its sharper and more pronounced, like the new CV shafts just eliminated some of the play, and now all of the play is happening in one spot.

Could this be the differential??

[jlevie]

Differential or drive shaft

[iamsam]

I did take the driveshaft out completely and inspected it, installed a new Guibo and put it back in... Is there an easy and sure way I can test the driveshaft and diff to see what is causing the clunking?