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      10-16-2012, 02:38 PM   #1
jjw2331
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Drivetrain (Driveline) Slop or Loose

Lately, my car has been having this weird case of driveline slop. I can feel a thud in the dead pedal through my left foot half a second after I 1) let off the gas abruptly (or quickly) in a high gear (4,5,6) cruising around 2,000-3,500 rpm or 2) shift from 2nd to 3rd gear.

I know this car is known to have a clunky gear box, and I still have the clunks when I first drive the car cold. That's no surprise to me. However, this issue is noticeably different since I can feel a small thud from the dead pedal and my seat. I have also noticed that my cold start and idle have significantly more vibration than before. It's slightly rough on cold starts but during idle its faint. You can still feel vibrations in the wheel, my seat, and on the pedals. It's most likely not the diff bolts because I had a sheared bolt before and know that sound and feel.

My diagnosis is bad motor mounts (either torn or flattened, not broken). However, when I took it to the dealer, they said the mounts look fine. I even took a peek at the mounts and can't tell if they are bad...

Do these symptoms indicate bad mounts? Does anyone have this same problem? Anyone know what else it could be? I know for a fact that this driveline slop is not normal. I drove a 2009 e90 M3 at the dealership while I waited and did not feel the small thud I've been getting in my car.

Now that I've noticed it, I can't ignore it and it's really really annoying.
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      10-16-2012, 04:54 PM   #2
italyix
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Check my sig...and i still have driveline slop like you have described.
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      10-17-2012, 10:35 AM   #3
jjw2331
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Quote:
Originally Posted by italyix View Post
Check my sig...and i still have driveline slop like you have described.
Interesting italyix. I would have thought those mounts would reduce the slop in the driveline... By the way, how do you like the mounts? Are you using your car as a track car or DD?

To add to the weirdness, the slop feeling went away last night driving home from work. I tried to induce it but nothing (cruise around 50mph in 4th gear, push down the gas pedal for a few seconds, and lift foot off pedal). Tight as a drum. I'm starting to think now this might be an engine issue. Possibly the throttles aren't closing smoothly causing the jerk and allowing me to feel the inherent slop in the driveline.
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      10-17-2012, 12:37 PM   #4
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I really like the mounts, there is definitely added vibrations at really low rpm and they go away as the revs climb. I use the M as a DD, as it seems every time there is a track day I'm either at work or busy

Although I cannot seem to get rid of this werid vibration/shaking every time i accelerate below 2k rpm. It feels like something is out of balance. The problem has existed pre and post mounts.
Maybe the throttle bodies might be dirty, cause stickiness?
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