Clunking from rear end

[Digitalwave]

I've had this problem probably since I've owned the car, but its gotten worse lately. When I am on the throttle and I lift completely, or when I am off throttle and I hit it, there is a clunk that happens only once each time. It's coming from the rear end for sure. It sounds like something is preloading and releasing when I get off the gas, or unloading and then preloading when I am off the gas.

I've jacked up the car and checked the obvious a couple of times and never seen anything. My driveshaft is in good shape, and last summer I replaced the subframe bushings and everything is secure in the subframe. The only real thoughts I have are worn trailing arm bushings, or a loose diff. I am also going to check that all the bolts from the axles into the diff are tight. I don't have any spring pads in the rear either but I know my springs aren't sagging at all so I doubt they'd make a clunk noise.

Thanks for any advice.

[Charlie]

Dumb question, but since I didn't see you mention it, did you check the rear shock mounts?

Those are the most common causes of the "thunk" when they let go.

-Charlie

[Digitalwave]

No Charlie, but that is a good thought. While they were replaced less than 2 years ago, and there is no noise going over bumps at all (just when the weight off the car shifts due to large throttle inputs), its still a possibility.

[rwh11385]

I dunno, but let me know when you find out.

From reading bf.c threads, it is common for them to break their diff mount bolts, so check that. That might be it for me. And maybe tighten down the diff bolts holding it to the subframe. possibly we didn't get them tight enough and now a little loose, and it shifts around when we throttle on/off.

[Digitalwave]

I dunno, but let me know when you find out.

From reading bf.c threads, it is common for them to break their diff mount bolts, so check that. That might be it for me. And maybe tighten down the diff bolts holding it to the subframe. possibly we didn't get them tight enough and now a little loose, and it shifts around when we throttle on/off.

Do you have the same problem Robert?

It really seems like the diff could be a big possibility. Last time I checked, the bolts were "tight" and I had installed them with Loctite when I put in my 4.10 LSD, but that doesn't necessarily mean they are tight enough to stop slight movements. I'll check that big bolt as well (and the bushing, but it was good when I installed it).

[rwh11385]

refraining from thinking of a sarcastic and unnecessary way to reply because i don't see the point in this thread:

yes. i got the same or similar.

edit: and it's not RTABs, RSMs, diff bushing as they are new.

[nando]

my car does the same thing. I've been thinking that it's my rear driveshaft u-joints. RSMs are fine (last time I checked anyway), every other bushing is new. checked my diff mount bolts (I've also heard that they like to back out), they are all tight. maybe it could also be the rear diff? that seems unlikely to me though. and it seems to get worse when it's wet for some reason (much easier to break rear traction in my car in the rain).

[Digitalwave]

my car does the same thing. I've been thinking that it's my rear driveshaft u-joints. RSMs are fine (last time I checked anyway), every other bushing is new. checked my diff mount bolts (I've also heard that they like to back out), they are all tight. maybe it could also be the rear diff? that seems unlikely to me though. and it seems to get worse when it's wet for some reason (much easier to break rear traction in my car in the rain).

This even happened when my car is auto, and its a different driveshaft now obviously but the thing is about the same and there is no play in the driveshaft that I can feel. Maybe its excessive play or gear lash in the diff? It seems too loud to be that though.

[Red325es]

I have the same noise , my noise is differential backlash. but I dont have the
money for a rebuilt diff, or have the time for trial and error pinion depth
adjustment.

-pete

[erik325i]

I have a simmilar clunking noise in my car. It really bugs me because i hate it when my car makes unwanted noises.

I hope someone figures this out.

[golde30]

I have the same noise , my noise is differential backlash. but I dont have the
money for a rebuilt diff, or have the time for trial and error pinion depth
adjustment.

-pete

i would say this is the culprit for most. i had a similar noise on my old datsun(along with every other datsun owner) and it was always the diff...

[cheades]

Mine does it just when starting out in first gear, pretty sure mine is in the CV joints though. Had mine up on the jacks and you could feel just a little play in the joint, might want to check that as well.

[I_like_E30]

mine does a clunking noise when the rpm go below 1.5k (slowing down) but not always, it only does it when i slow down. I feels like something is disconnecting and connecting

[Digitalwave]

mine does a clunking noise when the rpm go below 1.5k (slowing down) but not always, it only does it when i slow down. I feels like something is disconnecting and connecting

Thats the same sound I get it would seem, but mine happens at any rpm.

[Mot]

lol I have the same noise too. I was wondering what the hell was going on. I'll check all the culprits listed.