Edwill

Hi!

This morning that irritating hum behind the instrument panel (my V8 is too loud to hear exactly where it comes from) appeared again! Right after gear shifts and fading away as the car slows down.

I read a couple of posts and fear that it could be the torque tube bearings, so me and a work colleague jumped into the car a while back to further investigate, but no sound appeared - even after a 5 km drive testing all possible ways of driving.

The difference - with the latter drive (the one without the hum) is that the car has been standing in the sun for about 5 hours.

SteveG

I've heard it described as a "rattle" most noticable at low rpm so as to eliminate competing sounds, sitting in driveway with door open head lowered to middle of car, clutch engaged. I have it, and have driven 1,000 miles with it. It seems to progress very slowly, but it isn't intermittant. If yours is coming from dash area, I don't think it is the tube. HTH.

DG84S

If you don't hear it coming from under the middle and rear of your 928 while idling in neutral/park, it's not the torque tube. Sound from the front makes me suspect, idler pulley, air pump, a/c compressor, alternator, water pump, fan, oil pump, frayed timing belt, or TB tensioner. For peace of mind, I would spend an upcoming Saturday looking for the source.

Red UFO

Could be your pilot bearing. Mine just went out and I heard some rattle a couple of weeks before the whole thing melting into nothing. Its a cheap part to replace if you have to.

Edwill

Thanks guys, I've been looking at the prices of rebuilt turque tubes, and they don't come cheap. So I'm glad it's not that.

It is something that's got something to do with gear shifts as it just happens after gear shifts (re-reading this sentence makes me wonder why I repeat so many words). Water/Air/Oil pump or the alternator will probably hum the whole time if it was that? A/C is not on.

Can anybody tell me where the torque tube is situated, just for interest's sake?

Garth S

Well Edwill,
It seems as if you have one of the rare 'Hummers' : (there's an even more rare varient that accompanies the hum with an occasional bell - like flat 'ding', there being known as 'Hum - dingers").
As to the source of the 'hum' - strange that it dissapeared with someone in the passenger seat: The first thing I'd check would be the mounting bolts and back rest pivots on that seat - seriously. Cabin internals can readily pick up and amplify any source of vibration, and be very difficult to track down.
Do you feel any vibration in the steering wheel? - is the hum sensitive to anything else you've noticed, like pressure on the steering wheel? (there are bushings on the steering shaft, that if worn, may transmit a resonant frequency). ie., it could be many things, most of which are simple.
The first thing to assure that all is OK under the hood, is to use a length of hose as a stethoscope and check everything out (ie., alternator bearings, but loose alternator mounting bolts as well, .....).
As to pilot bearing(s), if you have an auto, there isn't one.
The torque tube ( called 'central shaft' in the WSM) is that ~1.5m, 75mm diameter tube connecting the engine to the transaxle (transmission) - the 25mm 'drive shaft' within spins on 2(auto) or 3(manual) bearings: When the bearings fail, aka 'torque tube failure.
With any luck, perhaps the cure to the hum is to travel with an extremely attractive companion of the correct weight - in the passenger seat.

Cameron

Has anyone rebuilt their torque tube using the Jager replacement bearings?

.....Cameron
'91 Euro GT

Cameron

Has anyone rebuilt their torque tube using the Jager replacement bearings?

.....Cameron
'91 Euro GT

Edwill

Garth,

The sound did come on once with a fine female counterpart in the passenger seat. Maybe it's my car's opinion of the person. Or maybe she sees females as a threat to my devotion....

rob rossitto

when my 85Shark's torque tube bearings were turning to dust, all I heard was a metalic chirp or high pitched clunk on acceleration from a dead stop & occasionally as I was coming to a complete stop...sounded like it was coming from the front end or at rear of motor...local wrench had me replace motor mounts, ball joints, tie rod ends, trans mount, springs & shocks, steering rack, and finally tried telling me to replace rear 1/2 shafts too...but when I checked them they were fine....after he fried my auto 1st gear "testing", I took shark to trans guy, who pulled torque tube after my 3rd request ("but it looks fine"), front bearings were dust....nice & quiet now...