Violent Clunking/Vibration from Rear

[c0rbin9]

Usually I'll drive out of the neighborhood with everything fine. At some point along my journey, usually about 10 minutes after setting off, maybe after a downshift, a violent clunking will develop from the rear end. The clunking repeats, but in no set pattern - think bangbang-bang-bang-bang-bangbangbang, etc.

The best way to describe what I'm feeling is it feels like I'm going over a poor road surface, and I can feel the car hopping, particularly through the back of my seat, except the road is perfectly smooth. It goes away completely off throttle, and returns with throttle. I can feel the clunks through the whole chassis - feels very unnerving.

I just replaced my guibo and CSB, thinking they were the issue, but I'm still getting this. U-joints seemed solid.

Any ideas?

UPDATE: It was the CV axles. I replaced them and the clunking is gone, along with the car feeling much smoother. Guess it makes sense, these just weren't on my radar as they had supposedly been replaced by the PO.

[7pilot]

you'll need to have a butchers..
could be differential mount bolts loose/AWOL, busted center support bearing, trans and engine mounts.

m

[Seawolf]

Check all the obvious stuff....driveshaft, axleshafts, struts, diff bolts and mount, tranny mounts.

I did come across a car that exhibited the same problem a couple of years ago: Random sever banging from the rear end that came and went for no apparent reason.

Turned out to be a parking brake shoe securing cap and spring were floating around in one of the rear hubs, the securing cap occasionally jammed under the loose brake shoe and partially engaged the parking brake shoe, it felt like an axle shaft had broken loose.

Maybe worth checking if nothing else shows up.

[TobyB]

Rapid- fire regular banging, or occasional, clunk, pop, p-tooie?

It's not so common with the 188mm diffs,
but if you don't find anything else wrong,
the ring gear bolts make a real racket when they start backing out.
I've always looked by taking the rear cover off, but you might be able to see through
the speedo sensor hole...

t

[c0rbin9]

I put the car on jack stands and inspected this morning - only thing amiss was that both axle shafts had torn boots (pretty much completely gone). Tranny mount, guibo, CSB are all brand new. There were also no loose diff bolts.

Interesting about the parking brake, seawolf. The PO disconnected the E-brake, but only on the left side. The right side is still connected and engages somewhat - that could be it! I'm going to disconnect it and see if it solves my issue. Is there an easy way to do so?

When the banging starts, it does it constantly when on the power, but not in a set pattern. Hope that makes sense.

[Seawolf]

The PO disconnected the E-brake, but only on the left side.

How did the PO do this ? If they just cut the cable then I can pretty much guarantee that the cable actuator pin is floating around in that drum.

I'd take a look in the left side first to see what's in there.

[TobyB]

Agree- rule out (and fix) the parking brake.

But if you have a 318, you also may have a 168mm
diff, and those do sometimes loosen the ring gear bolts.
And doing it on power would suggest that- IF you find nothing else...

t

[c0rbin9]

I think it's something to do with my diff or CV axles.

[uturn]

I say muffler rubber supports are out!

[c0rbin9]

It's definitely something in the driveline. The car is my only transportation to work, so I have had no choice but to drive on it. It only starts after about 15 minutes of driving.

The "banging" is not just a sound. The car judders and vibrates.

[Kershaw]

Next time it starts shaking, pull the handbrake a little and see if it changes.

[c0rbin9]

We're on the same page Kershaw - in fact, I've been doing that - no change.

The issue has morphed from a distinct banging to an only slightly perceptible vibration. Now instead of the car screaming that something is wrong, something just feels ever so slightly "off". Great.

I'm going to try to bring it to a shop tomorrow as I've exhausted my mechanic abilities on this one. Hopefully they will have an informative diagnosis, though I'm not too optimistic that they'll be able to pinpoint the issue. I can hear myself now "No, I don't think it's the driveshaft."

[c0rbin9]

Talked to a shop - they seemed confident in being able to diagnose the issue and I know they have experience with E30s, so I'm feeling optimistic. The price on the other hand...

[Boris3]

7pilot also had engine mounts on his list, are those new as well? Didn't see that on your list. Reason I ask is that one or more sheared motor mounts will lead to the symptoms mentioned.

[c0rbin9]

So the shop said they weren't able to test drive the car because liability or whatever with a corded rear tire. And they wrote me a $4500 estimate for all the shit I already knew was broken. It "might be" the CV axles, but they don't know because they didn't drive it. That was pointless.