Big Time Poster
grinding sound when coasting in gear
this has been driving me nuts ever since i took her home back in the day. When I'm coasting in gear (no pressure applied to gas pedal) there is a loud whirring/grinding noise. When I'm coasting in neutral or with even slight pressure on the gas this noise isnt apparent. Any ideas? It seems much worse now thats its finally cold here
'90 535i
UUC SSK, Bilstein shocks, Eibach spings, EAT chip, CAI, Super Sprint exhaust, Hella euro headlights, HID kit, M5 spoiler
Grand Master
Worn diff is my guess. Make sure the right oil is in there and the right level. In my limited experience, rear ends can be noisy for a long time before they break, and some noise is normal.Originally Posted by BigTed00
When in gear and no gas applied, the wheels are driving the drive train and you hear the noise from the final drive, even if you're in gear w/ the clutch depressed you should still hear it.
Bright side: may be the excuse you need to upgrade to a better diff.
Robin
72 Chevy K10
01 E39 M5
Green Beret Special Ops
could also be the center drifeshaft bearing. Time to inspect.
95 E34 530I V2.37
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Those who make peaceful revolution impossible will make violent revolution inevitable.
John F. Kennedy
3 Grand Master
Drain the rear end and see if it dumps any metal filings. You may also want to get a magnet on a stick and run it up towards the pinion, pull it out and see what you've got.
Major Contributor
What about rear wheel bearings? I had the same issue - replaced the Rear Wheel Bearings and it went away - JT
Big, Big Time Poster
If the noise only appears during coast situations, where the rear wheels, diff and trans are driving the engine, I am inclined to say you have diff or rear trans bearing problems. If you had center driveshaft bearing problems, it would tend to talk to you all of the time but give it a look see either way.
You haven't been jerking second gear to squeel the tires have you?This causes a 'hammering' situation on the rear trans bearing, which dents the bearing race, causing a nasty racket (and an emptier wallet to replace the bearing).
By the way, I wouldn't know anything about this personally.
As bad as the above is, it is much cheaper to fix a bad rear trans bearing than a bad ring and pinion gear or bad pinion bearing in the differential (another symptom of jerking shifts). Trust this level of repair to only the best. Setting up a ring and pinion takes knowledge and patience. Done wrong, you have trashed the ring and pinion set which makes my wallet wince just thinking about it.
I doubt bad wheel bearings would cause this but should be easy to verify. With the car at speed on an empty road and coasting in neutral, load each side in turn by weaving back and forth to shift the cars weight from right side to left and back again. The idea is to add weight to the rear wheel bearings one side at a time to make them 'talk' louder. If this 'loading' has no effect on the noise, your bearings are solid. If one side talks loader than the other, time for some wheel bearings or tires if they are cupped from a less-than-stellar alignment.
Good luck,
Brian
Big Time Poster
Brian,
Thanks for the great reply. While it doest seem like wheel bearings ATM, at 188k miles on original bearings I wouldn't be surprised.
Can anyone elaborate on the rear transmission bearing failure? I did a search of the forums but couldn't find anything. It may be a differential issue, but who knows
'90 535i
UUC SSK, Bilstein shocks, Eibach spings, EAT chip, CAI, Super Sprint exhaust, Hella euro headlights, HID kit, M5 spoiler
2 Grand Master
check your driveshaft, ds center bearings and such. i had a very similar problem and it ended up needed a new driveshaft. manual swap time.
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