SICAMG

This has be coverd many times but still looking for answer. I have a 2005 E55 thats had this noise for 9 months and is getting louder ...mostly on the right side on certain bumps.
Replaced sway bar links, bushings, removed factory air suspension and installed coil overs with brand new lower controll arms. Just did rear subframe bolts to be pro active, bigger bolts with steel plates and nuts on top, rewelded all back togather, and replaced front bushings for the hell of it but did not need them. Removed rear spare tire and taped down rear seat head rests. Car sat a while to do custom fuel rail and filter install/project and this morning on first drive....still there like nothing done to rear suspension. All controll arms where also removed on that side to check bushings as well.
Only way to lessen the noise is to set rear shock on soft settings.
Funny thing is I am teaching suspension systems this term in school and cant even fix my own car...not even with my own guys at my dealer at work at on the side. Any help would be great, Thanks

TheTherapist

Have you checked the diff mount? Torque can rip it out the then it settles back in the hole where it's not immediately obvious except you know something feels wrong and it can bang at times over bumps depending on where it's currently sitting. Had me baffled for a while - I ended up replacing bushes and shocks/baffles before we noticed the real problem one day when under the car.

SICAMG

Wow never really looked that hard at the diff. I will throw it on the lift today and see. See.... thats why I love this site. Complete wealth of information!!! Thanks
PS never looked to much at thet because the bumps where so minor to make the noise I couldnt see that being an issue. I will keep you posted.

TheTherapist

Denroll ripped both his out at the same time! That's when you know you're getting respectable horsepower to the wheels lol. The good thing is it's easy to repair stronger than it was before.

shardul

iTrader: (1)

you will need to replace the shock absorber to eliminate the thud.

SICAMG

All shocks are brand new....brand new coil over set up. Even swaped to another set of shocks in the rear to be sure, no difference.

MomentumE55

Shardul I want to get rid of this also. Is there a way to diagnose rear shock? The fact I have 125k on them makes them suspect. I also have lowering links and 20" 10.5 with 305's on rear which I thought was the cause. Car came with these so never was able to determine onset of thud. Love the car but hate driving it because of jarring thud on any decent size bumps while cruising. Never can use sport settings because it is then unbearable. There are no fluid leaks on shock and bounce test by pushing down and releasing on trunk of car is inconclusive as it barely moves. I would GLADLY spend what looks like nearly $1,000 for parts alone for two rear shocks if it would improve this issue if I was sure it would " help".

shardul

iTrader: (1)

can you change the dampening on the shocks?

shardul

iTrader: (1)

you can inspect the shocks for leaks etc. Majority of the times when the shock s have been replaced the problem has gone away

chawkins2001

Have you checked the trunk for a dead body, solved a few members issues when they heard the rear thud. Just a thought

MomentumE55

Does sound like a dead body flopping up and down back there! Don't ask me how I know haha. I'm off to buy some shocks, I'll spend a grand, it has to make some difference. Thanks guys.

SICAMG

Yes. When set on soft it gets very quiet. If set on normal to stiff and its very cold ,it really thumps. I just asuumed less impact on the suspension when on soft and thats why it gets quieter.

Max.H

So, is this thud an issue with diff mounts or shock absorbers? I only get that going over speed bumps.

Can it cause other issues if left alone?

shardul

iTrader: (1)

most of the time it is shocks

kponti

Trans mount. I thought mine was the rear shocks too and after new coilovers I still had that sound. Trans mount later it went away.

Only made noise when I hit bumps. Got worse with coilovers especially when I set the shocks to stiffer. Seemed louder in the cold (but that could have been my imagination)

TheTherapist

Trans mount or diff mount?

If it was the trans mount that's a new one? Surely that issue would have manifested in other ways also like clunky changes?

SICAMG

Too busy at shop so Wed. will go on lift. This morning verified that left and right side will do it {right side louder}. Its a very quick knock/thump when something like a man hole cover set 2 inches below the surface is driven over. Every day its the same bumps and every day same thing. If you do not hit a bump that is quick and abrupt...it will never happen. I will start with the differential and if nothing pull the shocks out and drive it to see. Trans mount new by the way.

SICAMG

Diff is very tight and solid. Guess I will live with it because it is not a safety issue.