Hey, I have a 2006 non-s cooper with manual 5 speed and 111,000 miles.

It's been making a terrible sound from the transmission, a knocking or grinding I guess. Wish I had recorded it before taking it apart.. oh well. Sounded almost like an exhaust leak, and early on thats what I thought it was. Soon though (a few weeks maybe?) and it started to get loud enough I started paying more attention. Early on I only heard it while accelerating, and a bit while decelerating at high RPMs.

Soon it became loud enough I could hear it all the time and realized it was related to wheel speed. It makes the noise all the time, even when coasting with the engine off. It's quieter while coasting, but there. Loudest when there is power from the engine, either to accelerate or decelerate. In the sweet spot in the middle when RPMs match the current speed it gets quite again. It seems to be about one crunch per wheel rotation.

I thought it was a wheel bearing, so I changed that but no luck. I thought it might be CVs, even though it is unaffected by turning, changed the drivers side axle but no luck. With the car on stands I was able to put it in gear at idle and listen from underneath. Definitely coming from the transmission.

Pulled the transmission and opened it up, first time for that for me. Expected from how terrible the noise got the last few days while I was fixing other things that there would be a pile of teeth in the bottom, but no. There are a bit of shavings on the magnet, but no chunks. No bearings appear to be falling apart. Nothing bad inside the differential. I have not been able to check the bearings on the back side of the gears since I have not yet figured out how to get that apart, but I can't see anything majorly wrong.

Is is possible bearings can make such a loud noise, and could it be about one per rotation rather than more constant, like a whine? Any other ideas? Should I just scrap it and buy a new one? Should I put it back together and have it rebuild?

Thanks,
Bryan

 

Here's the only odd thing I've found so far, the rough spot on the end of the shaft.

And here's whats on the magnet

 

Hope you found source of noise. Hard part will be figuring out why that galling occurred. Maybe just old age!

 

Related to load = no wheel bearing
Goes with car speed = from secondary "downwards"

Very likely a bearing IMHO, just go for a 'box rebuild and you should be fine.

 

Bryan,

What was the final result on this? Was that worn shaft the culprit or was it something else? Experiencing extremely similar situation here..

-Zac

 

Never tracked it down any farther, ended up just replacing the transmission and that fixed the issue. Decided it was beyond my skills to try to fix anything inside the transmission.

 

I was afraid youd say that.. I appreciate the reply.

-Zac