Squealing/Screetching when I shift

[78silver]

I've noticed that lately I'm getting a faint squealing sound in between shifts when coming off the clutch and onto the gas. It's not a grinding sound or feel but more like a squealing belt but from under the car in the transmission case.

Any thoughts/ideas? Shifts fine otherwise.

[kach22i]

Is it at all possible that the sound is always there but the sound of the engine is masking it?

[turn6]

could it be the clutch is down to the rivets?

[78silver]

No, I would have noticed it before. Something else interesting is that it only seems to be there when cold and then seems to go away after the car has warmed up a bit.

I've not replaced a clutch before but to me the clutch feels pretty solid... how would I be able to easily tell if the clutch was down to the rivets?

[kach22i]

Originally Posted by 78silver

.. how would I be able to easily tell if the clutch was down to the rivets?

I don't know, every clutch I've had let me know it was going by slipping a lot. Do a search if "turn6" does not get back to you.

Perhaps a transmission mount is going. The engine hangs off the transmission, if the mounts are bad everything would move in unexpected ways.

I read a little of the 101 Projects book last night. They said if you place a wood block on your floor jack and raise the car under the circular engine drain you can jack up the car, then place jack stands under the two tubes sticking out (torsion bar covers). The comment made: If the engine raises slighty before the rest of the car the transmission mounts may need replacement.

[turn6]

well, one of my cars does this when it's cold and the car has ~148K on the original clutch that does not slip and the motor is strong. Usually happens when i'm wearing flips ;-}

[78silver]

OK, well now I'm getting really concerned.

Was driving into work this morning... got the same brief squeal (almost like a chirping) between certain shifts... seemed to go away after it warmed up a bit. Then as I was exiting the freeway moving fairly slow in 3rd gear (probably at about 2500rpms), I heard a "kaplunk kaplunk kaplunk"... at first I thought I ran over something but then realized it was coming from right behind me in the engine compartment... basically sounded like I lost a belt and it flopped around a couple of times before falling off... after a few seconds of that it got quite and all seemed well. I pulled off very quickly and killed the engine in fear that it was my alternator belt. To my surprise both alternator and compressor belts were still intact and both seemed to still have the right amount of play... however the alternator belt was extremely hot and it looked like it had slipped for a bit burning off some of the rubber... there was some black "belt ash" on the fan.

Anyway, I cranked it back up, everything seemed to spin fine so I headed on into work without another issue.

Any thoughts on what the sound might have been?

[ed martin]

Perhaps you don't have enough tension on the belt and it is slipping?

[kach22i]

Before I got the hang of it and started using some sticky stuff to hold the alternator fan belt shims in place, I bent a few space washer shims. What would happen is they would slip and the belt would slip as it was not turning at a proper true angle. It was hard to tell anything was wrong from the small amount of slippage until I took it apart again and re-flattened the shims or put in new flat ones. Maybe, just maybe the shims or belt was put in wrong last time.

I know the "101 Projects for your Porsche 911" book gives fan belt replacement one mechanic/star for difficulty, but that does not mean it's not easy to screw up.

[DaddyGlenn]

Anybody think about the throwout bearing?

Could it have a rubber centered disk that is falling apart?

Slipping belt that only squeals when the engine rpm changes rapidly i.e. during a shift?

[DaddyGlenn]

"I heard a "kaplunk kaplunk kaplunk"... "

Did the sound match the frequency of the engine or tires?

[kach22i]

Originally Posted by DaddyGlenn

Anybody think about the throwout bearing?

Could it have a rubber centered disk that is falling apart?

Slipping belt that only squeals when the engine rpm changes rapidly i.e. during a shift?

My money is now on the throwout bearing theory.

I thought only 964's had the rubber disk though?

[ed martin]

The throwout bearing would make noise when engaged/shifting so that makes sense, but that wouldn't make the noise described (schreeching, sqealing). Sounds like a belt.

[Early_S_Man]

Pilot bearings tend to screech when the needles are running dry [rather than in a good coating of moly] and/or rusted. You only hear it with clutch pedal pushed in ... in neutral or between shifts ... because when clutch is engaged the transaxle input shaft isn't turning with respect to the pilot bearing!

[DaddyGlenn]

Originally Posted by Early_S_Man

Pilot bearings tend to screech when the needles are running dry [rather than in a good coating of moly] and/or rusted. You only hear it with clutch pedal pushed in ... in neutral or between shifts ... because when clutch is engaged the transaxle input shaft isn't turning with respect to the pilot bearing!

I was thinking about that but didn't think the sound would be audible over the engine.