dvdt

Hi All

Car developed a strange issue recently. If i accelerate slowly it feels normal, but if i give it a bit more i can actually feel a grinding feeling through the floorboard!

I replaced the motor and trans mounts about 5 months ago, and the carrier bearing about a month ago.

Could it be a failing u-joint? Any ideas welcome!

CLKCLK

Check the driver side down pipe clearance (right at the curve). It may touch the floor when you have too much torque or your engine mount goes bad.

GL

novae500

i have this as well when i stomp on the gas...Thought it was the headers rubbing but not, bad wheel bearing, not. replaced by leaking power steering pump last week and seemed to go away.

vioilio

Do you have long tube headers?

dvdt

Nope, bone stock.

James M

Does this problem happen in 1st gear only on hard take-off or all the gears?

dvdt

Any gear if you give it enough throttle!

dvdt

I'm thinking there is a small possibility that one of the nuts came off of the top of the motor mount, and now the motor is pitching over when under load.

I torqued those things as best i could but damn was it hard to get good leverage up there!

mobhouse

This is happening to me now too! I'm figuring its a mount because if i let off after doing so and it shifts up, i get a loud slam.

kalyons56

Hello,

Has any one found the culprit for this issue?

I just picked up the cls55 2 nights ago. The test drive was perfect and I was very conservative during the test drive after I signed all the papers and left I smashed on the gas and got the same vibrations under the floor board described. Anyone know what this is?

Any help would be appreciated!

biggking

Miles? Check wheel bearings, and also check the rubber flex things on either end of the drive line as they as super common. Driveline shouldn't be going bad but it won't hurt to check the center coupler piece thingy in the middle of the drive line.

kalyons56

Thanks for your response. It has 73k miles.

Will definitely have your recommendations looked into

BagMan

Check the motor mount bolts both sides, top & bottom. I had this problem when the dealer forgot to reinstall them after working on my car.

These bolts seem fairly week also. I snapped one by hand during an install not too long ago. So, maybe it broke.

The lower bolt part number is 2209902201

shardul

iTrader: (1)

can you check the differential

vioilio

What exactly in the differential?

shardul

iTrader: (1)

rear diff

vioilio

what exactly is one suppose to look for in the rear differential? A friend of mine does have this exact same issue

biggking

Motor mounts are way different when they are bad. I had issues where the entire car lurched at a stop or take off. I also had some vibrations due to a bad transmission mount (20 min to replace on a lift) and also I changed my end rubber pieces for the drive line (they were cracked). I honestly think it was the transmission mount, I have actually replaced one earlier today and the car had major vibrations and it sounded like a diesel on take off. After we replaced the mount ($60 from MBZ i think) the noise and vibration went away. Upon initial inspection of the car we could not tell that the rear transmission mount was bad. Once we removed it, the play was insane.

shardul

iTrader: (1)

also check drive shaft flex plates

biggking

Totally forgot what they were called. Thanks for that.

shardul

iTrader: (1)

guibo for BMW folks

biggking

Yea, more like my sub frame might fall off first though

shardul

iTrader: (1)

sometimes if the cats are blown out you will get a vibration on the floor board at WOT

BagMan

I had a missing motor mount bolt and had the exact same symptoms described by the OP. Car felt normal until I floored it, then there was a vibration under the driver's footwell.

It took me a while to figure it out, but it's a easily identified visually.

mobhouse

Had this same issue around 77k miles and found out it was my motor mounts/ transmission mounts. drives perfect after replacing them