Rear end knocking 325i sport

Tue Jan 24, 2006 8:59 pm

Hi all, after a bit of advice on my E30 325i sport.

There is a knocking noise coming from the rear when cornering slowly and tight, the noise stops when you accelerate.

Anyone got any ideas?

Tue Jan 24, 2006 9:10 pm

presumably the car drives straight and doesn't have any bush issues? Doesn't wander about at the back end etc?

check strut top mounts. check exhaust system is not fouling anything, battery is anchored down, jack and any other items are not flying about

Tue Jan 24, 2006 9:18 pm

I can rule out items in the boot as it's empty, the knocking is only at low speeds.

Tue Jan 24, 2006 9:31 pm

Can you be a little more specific about the noise,
Is it over bumps? is it regular or sporadic? does it come from the center at the rear or from either side?

Tue Jan 24, 2006 9:39 pm

I noticed it more after a motorway journey, it seems to be coming from the outside (wheel side) on both right and left turns. a constant knock.

Tue Jan 24, 2006 9:49 pm

my money is on it bein a drive shaft but need more details really?

is it constant or only when turnin???

get worse with speed???

braking affect it???

Tue Jan 24, 2006 9:52 pm

Only when turning, better with speed and not effected by braking.

Tue Jan 24, 2006 10:17 pm

Sounds similar to the noise I have been getting. Low speed only, a light clonking I would call it, but the car drives fine. Does it happen whether or not the car is in gear? If so I think it's more likely suspension or exhaust than drivetrain. That was the case with mine and I was advised to change shock top mounts and anti roll bar drop links. Did those and it's improved things but the noise is still there. Thought the diff mounting bush might be knackered (see my thread "Diff mounting bush") but after the feedback on that I havent gone ahead and changed it. Rear subframe bushes were changed on mine about 5 years (20k miles) ago so I have excluded those for now.

Hope this is helpful. For now I'm waiting for inspiration - post back if you get some!

Tue Jan 24, 2006 10:44 pm

I had a knocking noise on my touring although it occured over bumps and at speed, it was only on the left-hand side and at the rear.
Started to really wind me up last week so i put her up on axle stands and low and behold, the farthest postioned exhuast strap had rusted through and was flailing about the place in two pieces causing the exhaust to wallop the arch at speed or over bumps - at least I think thats what was happening.

Strap removed, good used one off ebay, knocking noise gone

!

I don't know if this is any good for you?

Wed Jan 25, 2006 10:32 am

could be the xhaust knocking on the spare wheel well. this is getting common on E30's.

if not, then i'd check your diff. if its knocking when going through TIGHT corners at SLOW speeds and when going LEFT or RIGHT, it might be a problem with the output components, or even from the sun and planet gears inside the cage???

there's a chance this is probably not the case, but i've known it before, so you gotta account for everything!

also, E30BeemerLad mentioned top-mounts. definately worth checking them...

Wed Jan 25, 2006 6:23 pm

I drove the car to work today (about 8 miles) and there was no sighn of the knocking, it only happend after run on the motorway, as if somthing had got warm.

The car has a full BMW service history up untill 2003 and i know the last owner so it has not been abused i bet the LSD hasn't had to do any work.

Checked the diff oil level today and it is ok and very clean.

I had a Carlton GSI with diff trouble but was told they only knock under load when turning, this one stops knocking when under load.

Hope it's just a bush or two.