knocking noise - United Bimmer Community

**max79** · 12-29-2007, 05:22 AM

hi guys .. i have 325is auto , i got it 2 month ago and since that i here knock noise under my car when i shift the gear from d to n ... after one month i begin to hear that noise when overdrive ( or shift gear4) is set ( after speed 80 km ) and if you driving the caron speed 120 km for example and remove ur foot from accelerator and accelerate again loud knock sound comes ... plz help ...

**Antiburn** · 12-29-2007, 06:23 AM

Bad trans mounts, center bearing or diff has excessive play.
Is the knock only once or constant

denyo77 · 12-29-2007, 08:50 AM

what year is your car? is it an e30?

**max79** · 12-29-2007, 11:55 AM

thanks for Antiburn and denyo77 for replay ......

only knock once ... but i think if there is any problem with center bearing you will feel vibration that i dont have at all ?... and my car is E36 325is 1993 ...

**Antiburn** · 12-29-2007, 01:56 PM

Best thing to start off with is get under there and see if anything is loose, worn or torn.
Hve someone in the back seat and see if they hear it comming from a different place, possibly underneath them.
My e30 if you get on and off it with quick blips while driving you can hear the slack in the diff knocking together, but thats only when you get on/off repedly.
The noise your hearing sounds like the same thing I have, but if your diff isnt grinding or howling I wouldnt really worry about it to much. A car with over 100k miles is going to make some noises.

**max79** · 12-30-2007, 01:01 PM

i think the problem with diff mounts coz my diff gose up and down when i shift from d to n or r ... and also the rubber mount that join the shaft with gearbox is damaged but have no lose ????