Rear end sounds really bad

i325 · #1 (**permalink**) 06-20-2009, 08:33 AM

Hello all. I have a small problem. its not as bad as the heading makes it to be though. when I go over a bump I can hear the passenger side rear make like a popping sound. I just got new shocks in december and I put on some meyel heavy duty rear shock mounts. when I did all that i put the shocks on opposite sides incase I had a bad shock. that didnt solve anything. it is only on the passenger side rear and when I go over a bump the back end sags a little on that side. can somebody please help me?

fiveightandten · #2 (**permalink**) 06-20-2009, 08:11 PM

Quote:

Originally Posted by i325

Hello all. I have a small problem. its not as bad as the heading makes it to be though. when I go over a bump I can hear the passenger side rear make like a popping sound. I just got new shocks in december and I put on some meyel heavy duty rear shock mounts. when I did all that i put the shocks on opposite sides incase I had a bad shock. that didnt solve anything. it is only on the passenger side rear and when I go over a bump the back end sags a little on that side. can somebody please help me?

So, you had the popping issue, replaced the RSMs and it was still there. Then you swapped the shocks from left to right and it stayed with the right side, correct?

When you swapped the RMSs out, did you carefully examine the shock tower(s) to rule out any metal fatigue or failure? Sometimes it can be hard to spot cracks. But that would be the first thing i'd double check.

This can also be a number of other things, including but not limited to:
-Swaybar tabs on the subframe are cracked. These are the mounting points for the swaybar itself and they're notorious for cracking and even snapping clean off the rest of the subframe.

-Broken rear ball joint. Inspect the ball joints (they look like bushings) on the outer connections of the upper and lower control arms. Try moving suspension parts and/or carefully prying things back and forth to see if you can spot any excessive freeplay or hear any popping like you're noticing when driving.

-Rear trailing arm front bushing pocket failure. The threaded bungs that hold the mounting bolts in can have their welds break and pull away from the chassis. Normally the force will just yank the whole bushing console out of the car, but it's possible one of them popped out and is causing the console to slap against the chassis. It's also possible you have an RTAB that's completely destroyed. Though they're pretty damn robust rubber and it would take quite a bit for it to be bad enough for you to hear it popping like that (aka the RTA slamming into the console under load).

-I'd also check the following things if the above items don't yield any positive results: Front diff bolt and diff mounts, drive axles for freeplay.

I really think this is either a bad shock tower, or an issue with one of your balljoints. Hope that helps.

BadGTho · #3 (**permalink**) 06-21-2009, 03:56 AM

i think nick covered it... check the above!

i325 · #4 (**permalink**) 06-21-2009, 10:47 AM

well all i know is that it wasn't as bad after i swapped the RSMs out. I will have to double check for the metal fatigue and hope my friend can weld in a crowded area. i would just go to TMS. and get their mild steel reinforcement plates if thats the case. how would I check the ball joint?

BadGTho · #5 (**permalink**) 06-22-2009, 09:30 AM

if you have metal fatigue the proper fix is to cut out the old tower and weld in a new one. the metal is very brittle and welding a crack is a short term fix.

to check the balljoints, jack up the car and shake on the back wheel.. then remove the wheel and shake the control arms... see if you have freeplay.

fiveightandten · #6 (**permalink**) 06-22-2009, 02:13 PM

Quote:

Originally Posted by i325

how would I check the ball joint?

Ben covered it pretty well, but to add...

The balljoints are at the outer ends of the upper and lower control arms. They look like bushings while they're installed. They are, however, balljoints, which means they pivot. Picture it like this...

A---O---B

The ball is in the middle. When A goes up, B will go down. When A comes towards you, B will go away from you. If the ball joint is worn or broken, you'll get either excessive freeplay, or you'll get a situation where A goes up and B goes up too. Either scenario isn't normal.

The suspension won't allow for tons of movement in an direction, so it may be hard to spot changes, but you can use some ratchet extensions of something to gently pry on things and poke around. Be very careful of the rubber boots on those things, they're pretty thin. You can disconnect the upper control arm to play around with it by hand. Do NOT disconnect the lower control arm. That one has an eccentric bolt that sets the camber of the wheel, disturbing it will alter the camber.

EDIT: It did just occur to me that you have an earlier E36, and therefore you may have a balljoint on the UCA and a bushing on the LCA. Take a look and see...if they look different, they are.

That being said, pull the carpet back from inside the trunk and concentrate on the shock tower(s). This is the most likely source of your problem. Pull the mount off completely again and check both the top and the underside of the metal very carefully.

Matthew C Smith · #7 (**permalink**) 06-29-2009, 03:43 PM

Gents,

On the rear of the e36 there are no ball joints. The hub fits directly to the trailing arm. This trailing arm attaches to the body with a bushing (RTAB). The lower control arm attached again with bushings (at the arm & at the subframe). The upper control arm (which houses the spring) again connects with bushings at the hub/trailing arm & the body.

If you look at the bushings and they're not cracked, falling apart, or the metal has seperated from the rubber material they are likely okay.

So how do the RSM's look? Increased damping shocks (Koni, Bilstein, Tokico etc.) put increased load on the RSMs. It could be that the ones you used weren't up to the task.

Have you investigated the other areas?

Matthew C Smith · #8 (**permalink**) 06-29-2009, 03:45 PM

Here's a seperated balljoint. Look to the right hand side of the picture for the shiny cylindrical part with threads on top.

Front Right Suspension

EDIT: Well for whatever reason, that link's not working for me. Try this MCS - Modification Tutorials: Bilstein PSS9 Coilover Installation

BadGTho · #9 (**permalink**) 06-30-2009, 08:56 AM

[quote=Matthew C Smith;1786817]Gents,

On the rear of the e36 there are no ball joints. The hub fits directly to the trailing arm. [quote]

untrue. there are balljoints in the rear... 4 of them on the newer E36s

02 Ball joint 2 33326775551
RealOEM.com * BMW E36 M3 REAR AXLE SUPPORT/WHEEL SUSPENSION

common misunderstanding because the balljoint is not a conventional type with a threaded end. it sits sideways and the ball is conceiled.

Matthew C Smith · #10 (**permalink**) 07-02-2009, 04:26 AM

Interesting. So it's a ball on a sleeve/tube arrangement.

It looks like the M3 (95 included?) used 2 per side as shown. The non-M e36 cars have only the top mount.

Thanks for the information.

BadGTho · #11 (**permalink**) 07-02-2009, 11:15 AM

Quote:

Originally Posted by Matthew C Smith

Interesting. So it's a ball on a sleeve/tube arrangement.

It looks like the M3 (95 included?) used 2 per side as shown. The non-M e36 cars have only the top mount.

It's my understanding the the 95 M3 only has one per side like the other 3 series cars.. it's the newer E36 M3s that have 2 per side.

honestly, i was totally unaware that this type of balljoint even existed until another member had his whole deal apart.

it's a unique setup for sure.. and like any other balljoint they do go bad and allow for movement.

Quote:

Originally Posted by Matthew C Smith

Thanks for the information.

my pleasure!