Rear suspension knock - any more ideas?

[Splod]

Hi guys,

I've had an annoying and persistent knock from uder the back seat area of my 320i cab for about 2 years now. It sounds like something heavy but hollow - and whatever it is, it's not hitting directly on the body as it's nowhere near loud enough. It happens at any speed, whether or not under power, but is most noticeable at slowish speeds and light loads eg pulling into a car park, 15 - 20 mph or reversing down my drive it might just clonk once. Sometimes I even think I hear it clonk when I start the engine and the car's not even moving, but I may be paranoid now. Often pasengers cant hear it - but it drives me mad. I would love to forget it but it's been there 2 years and I have tried replacing the following:
Prop shaft centre bearing
Prop front spigot bearing and flexible coupling
Rear shock top mounts
Handbrake shoes

I have also taken off the BBS centres as I've heard those can rattle, checked and adjusted the exhaust, emptied the boot, taken the back seat out....Nothing makes any difference!!!

The only things that I think are left are:
Drive shafts/cv joints
Diff itself
Propshaft rear UJ
Diff bush

I havent gone into the possibilities of the suspension bushes and I know the beam bushes are ok as they were done a couple of years back. It's a 1990 car but has only covered 54000.

Any helpful thoughts appreciated, cheers.

Steve W

[fowler]

have a look at you prop donut as this can make the prop knock at low speed ??
or a rear suspension top mount poss ?

[Splod]

Both of these already changed mate, cheers!

Steve W

[fowler]

check all bushes etc also check diff carrier as mine had a clunk and it turned out to be this as it had a split in it
but to me it sounds like either rear beam bushes or trailing arm bushes

[ChemicalAl]

I think I have the same thing - my car is an '86 316 coupe with 56k on it. I recently (3 weeks ago) got the rear sub frame bushes changed (just a pre-emptive thing - there were no noises/clunks etc prior to this, I was just told that the RHS one was dropping and worn!) and now this noise has appeared! It is a very subtle clunk which seems to be coming from the drivers side rear and occurs when I depress the clutch (sometimes) and when I slow down to a stop, with the clutch depressed.
I have done a number of searches on this and have found that it could be some of the following:
Top Mounts
Prop centre bearing
Diff bush
Diff
Prop Donut
Could the enlightened of you out there advise on this - does this list cover everything? Could the changing of the rear sub bushes moved something else out of whack (This noise has only started after they have been changed and I think it must be related, either that or it is an unbelieveable coincidence!)

[Splod]

Hi

I have kind of been living with this since my first post 2 years back! I don't think it's as bad as it was and the car has always passed MOTs, no problem. However, when I do get some time, I plan to change the diff bush as it's original and I have read that you get much improved axle location from fitting one from a later car (think it might be from a m3 or z3 but I can't remember). This may help but I probably won't get round to it for a while. I have changed top mounts, prop centre bearing and donut though, and these didn't resolve it so it's probably next on the list!

Good luck bud

Steve W

[hongkongfuey]

have you looked at the exhaust ???

[ChemicalAl]

Got it!!! Just got two new back tyres put on last week - Bloody technician didn't tighten the driver side rear wheel enough - hence the knocking!

A tad embarrassed that I didn't check this immediately, but problem solved without any money spent.....result!

[Splod]

Good news mate - hope the movement hasn't damaged the wheel!