Cabby rear shock mount

[mcbonio]

Next on my list of things to do is the knocking noise on the rear drivers body which I think is the rear shock mount.

The previous owner said the passenger side had been done as it started knocking too. But he can't remember what part they replaced only that is cost about a tenner.

I'm trying to figure out what part it might be, anyone have any idea what might be failing here? The sound is like someone knocking on the inner wheel well on the metal bodywork.

[mcbonio]

Heres a pic of both suspension areas.

[jmc330i]

I can't see the pics properly on my phone, but the mount in the bottom pic doesn't look genuine.

U need part 7 from the realoem pic. It will be more than a tenner though (even for E30 parts) so I'm not sure what was replaced before. E46 cab mounts are a direct replacement and stronger than E30 ones - I'd suggest changing both if they are of unknown age or quality. You can also fit part 10 which from memory is a strengthening plate from the Z3.

[mcbonio]

I'm guessing part 7 has some kind of bearing? Thats whats knocking away?

[jmc330i]

Not really a bearing I'd say. The shock goes through a metal tube that runs through the rubber. The rubber can either crack or the metal tube pushes through the rubber so its not connected to anything anymore. Either way, once its gone it needs replacing.

As pointed out in another thread, there is a link to the wiki for replacing the mounts in a touring. Obviously the boot trim access differs, but swapping the mounts is the same.

[Brianmoooore]

Part 7 is what needs to be replaced, and as said above, E46 cab. ones are identical in shape, size and appearance, but are stronger.
Part 12 in the lower pic. is not the correct part, so should be replaced, and make sure that parts 6 are in place (incorporated into the dust cover on standard dampers).
Very simple DIY job to replace; no need to even jack the car up: Unscrew the two 13mm nuts in each of your pics., undo the 19mm bolts that holds the bottom of the dampers to the hub carrier, and remove the damper and mount together. Hold the square section at the top of the damper firmly in a vice, and unscrew the big nut in the middle of the mount. Put it all back together, but do not fully tighten the 19mm bolt at the bottom of the damper until the suspension is at normal ride height.
Buy genuine mounts from BMW.

[mcbonio]

Will MEYLE Heavy Duty e46 rear shock mounts suffice?

http://www.ebay.co.uk/itm/BMW-3-E36-E46 ... 058wt_1163

[jmc330i]

Those aren't for the E46 cab, so won't be much better than E30 ones. E46 cab mounts are the same from the 318i cab up to the M3 cab. I'd stick with genuine from the dealer as Brian said. Pay a little more now, but they will last. Buying cheaper mounts is a false economy when you need to replace them more often!

[jmc330i]

Those aren't for the E46 cab, so won't be much better than E30 ones. E46 cab mounts are the same from the 318i cab up to the M3 cab. I'd stick with genuine from the dealer as Brian said. Pay a little more now, but they will last. Buying cheaper mounts is a false economy when you need to replace them more often!

[Blitz]

Meyle are very good.

[jmc330i]

^^^ Fair enough, as long as Meyle is oem quality, there shouldn't be a problem.

Heavy duty or not though, it states in the link above that those aren't for E46 cabs.

[mcbonio]

Ok, so I changed the rear shock mount for an e46 cab one. The old only didn't look too bad, a bit soft maybe. The shock itself was still really good, they were changed in 2009.

It hasn't cured the knock unfortunately, I've changed the shock mount, anti roll bar bush and drop-link.

What now? What can this fast knock-knock-knock be every time I take off?

-Mcb

[mcbonio]

Could my rear drive shafts be worn and be clicking when I take off? They are a bit clunky to be honest.

[BenHar]

If there is any play in the CV joints they need replacing (you can try greasing and reversing them if they are a bit dry, but clunks mean they are dead).

Ben

[mcbonio]

Theres left and right play, and as I drive along and the autobox shifts down I can feel them clunk on the downshift, never on the upshift.

New drive shafts?

[BenHar]

There are a lot of places in the rear end that can shows signs of play (ooh err, Finbah).

That clunk could be gearbox, propshaft, diff, halfshaft, wheel bearing, bushes, etc.

Get it up on axle stands and wiggle everything (ooh err, again).

Ben

[aceifty]

i had a knocking sound from the rear, came out to be my drive shaft. before i changed it i used to jack up the car (the side where the sound was coming from) put it in 4th gear and let the wheel spin for about 5-10 seconds, that would stop the knocking sound for a while and then do it again when the sound come. i ended up changing both the drive shafts. its been 4 years and no knocking sounds.

[mcbonio]

I might swap the rears over, see what that does.

Cheers guys

[mcbonio]

Ok was hoping I'd solved this, I changed the rear shock mount on my cab, has been great until today where the sound has come back with a vengeance....

What other parts of the top shock set picure below up can knock when worn? It only seems to knock when there rear end is pushed down or going to? So frustrating!

[/quote]

[Grrrmachine]

Did you fit the top washer plate when you fitted the mount, as per the Wiki instructions? If not, your new mount is probably ruined already.

[mcbonio]

Which part Grrrmachine? No 10?

[Grrrmachine]

As I said, it's in the Wiki:

http://www.e30zone.net/e30zonewiki/inde ... Components

No 10 in your link is a paper gasket

[mcbonio]

Yeah my installation looks just like that... why does it knock more than before?

[mcbonio]

Ok I took some videos this morning, perhaps someone can chime in and give their opinion/experience.!


First is with the tonneau open looking into the void for the shock mount. [at 7 seconds, 13 seconds and 16 seconds]




Second is inside the cabin at the back where the roof is fixed to the body. [at 7 seconds and 15 seconds.]




Any input is appreciated.!

[DanThe]

Looking at the first vid id say its not the top mount making the noise, check the anti roll bar links are not fouling anything, springs still intact? Defo sounds like a metal on metal noise

[mcbonio]

Cheers Dan,
I only changed the ARB bushes and Links about 6 week ago. They are all good.

As it only sounds the the car's weight is displaced to the rear I'm suspecting the spring, or spring perch and its rubber pads they sit on.

Gonna have to jack it up tonight and have a good nose around. So annoying.!

But if anyone has had this before please chime in.!

[mcbonio]

Ok so I've spent the last hour underneath the car spraying each bush with lithium grease and then testing the car. The fault is with the big round subframe bush, the rear beam looks corroded and has probably affected it.

I've give it a squirt with grease and its stopped the noise, I think I will soon need a new rear beam or the current one welding or should it be fine?

[mcbonio]

Can anyone advise?

[Brianmoooore]

Can anyone advise?

Yes! If those are rust holes, then park the car up and don't drive it until the rear beam has been replaced.
I've never seen anything like that!

[mcbonio]

Its strange as the other side is fine.! Where might I be able to source a new rear beam?

[Brianmoooore]

Plenty of rear beams around in good condition. Usually just a bit of surface rust around the area the diff fits through. Try 'parts wanted'.
Possibly some muppet removed a rear beam bush sometime in the past by burning it out, destroying all the paint in the area?

[mcbonio]

Maybe Brian, you can never quite tell, e30s have a habit of springing nasty surprises on your as you dig deeper into them..

I'm going to take it to a buddy of mine who is a welding specialist, so he can assess the level of corrosion and possibly clean it up and weld it. Not getting my hopes up but I'll explore this option first as replacing the rear beam is a job I just don't fancy right now, and a garage will charge dearly to do it...

Bah.!

[DanThe]

Just looks like the paint has started to flake off to me, not holed

[Grrrmachine]

Deffo looks to me like a burst paint blister than proper seam rust. I suggest you get a wire brush on the drill and attack it properly before buying a new beam.

[mcbonio]

Looks like i'll be spending my evening under the 325i again.. lol

I'd of binned this car off ages ago only I fall in love with her again every time I look at her.. ahem..

Anyway, I think the seam is compromised as this is what is creating the knocking sound.! I think its slightly split and the 2 edges are knocking together.! Its a metal on metal sound, look at the videos above..