Gear Whine - what's the problem?

[CarreraS2]

OK I'll fess up and admit this is for my '86 BMW, but the issue is likely applicable to any manual tranny, including a 911.

I get a really loud gear whine/howl, sounds like it's from the transmission (manual 5 speed).

It is most loud at light loads in the 2000-3000 rpm range. For example, cruising at 2000 rpm, need to accelerate a slight bit, give it a tiny bit of gas. It will howl/whine as the car slowly accelerates through the rev range.

When you let off the throttle, it's still there, but nowhere near as loud.

If I'm driving in gear kinda coasting (like very slight throttle, so little the car is very slowly slowing down), the noise is gone.

Put the clutch in, noise goes away completely.

Put it in neutral, noise goes away completely.

Started around 10K miles ago, increasingly getting louder.

The trans has probably 160K on it. I put it in the car when it had around 125K on it, and it worked fine at the time. Replaced the clutch, TOB, and pilot bearing at that time. So those components were all new less than 40K miles ago (although I'm not ruling those out because of that).

Shifts fine.

Any ideas?

[bell]

a good friends e30 had a similar problem, it ended up being a bad carrier bearing in between the tranny and rear end, does the whine go up with the revs or with the speed of the car?

[bigchillcar]

hmm..thought i wuz gonna be tellin' ya not ta drink that ****. you kan stil bie it in arkansaw, but iht putts uh hurten on ya..
ryan

[CarreraS2]

That's a good thought, those center bearing go bad fairly frequently. I'll check that out.

Hard to say whether it goes up with the revs or the speed of the car, because really it's both, since the noise only happens when the car is in gear. Therefore, with increased revs necessarily comes increased car speed (for any given gear).

[Dan in Pasadena]

SoCal911SC, If its functioned properly I would consider trying some synthetic fluid like Swepco or Redline in it before opting for a tear down and major work. I only mention this because I had extra noise in my old 944 transaxle and it was amazing how big a change this made. It doesn't happen instantly, say over the course of a coupl of tanks of gas but it quieted my trans and smooothed out shifts noticeably. If it doesn't work you aren't out much money.

[MBEngineering]

HI it sounds like the diff bearings are on the way out, drop the oil and check, i have fitted diffs at the dealer i used to work at with the same noise, the trani' you will find has ATF fluid in it, just check befor changeing it????

regards mike