Ducman82

in gear, going down the road i hear a strange bearing noise. load dependent. changes when the car goes over irregularities in the road.

i thought it could be the throwout bearing.. but when i press in the clutch noise stops.

and "sounds" like it comes from rear of the car......... in gear it makes the noise, neutral it does not seem like it does. .....

new super bearing......... so i doubt its the TT......

Black Sea RD

Sounds like the throw out bearing since with modulation of the clutch pedal it stops the noise.

Drop the front cover and have a look/listen when you are able.

Good luck with the diagnosis,

Ducman82

only does it when under load or "moving" won't do it in neutral with clutch engaged

Mrmerlin

in what gear do you hear the noise?

Ducman82

all of them. (never made it to fifth) but I'm sure it will. i need to see if i can get it in the air and running in gear and get a scope and crawl under and look/listen

Ducman82

put the car in the air. it won't make the noise in any gear........ it must need to be under a load. does that info help anyone?

next is to take the cover off and look. but what should i look for?

Black Sea RD

Reading your description of modifications done to your 928, it seems as if there has been a lot done to your transmission/rear end?

It could be something in them since it is load dependent. Might be the reason why modulating the clutch and going over road irregularities brings the noise.

Best I can do, maybe Dr. Brown can lend a better diagnosis.

Mrmerlin

what was the last thing you fixed before you started hearing the noise?

Ducman82

i was thinking on that. i did some Trans cooler work (adding a late model cooler to an early car, cooler and lines to the back made.

actually the transmission is the only part i never fully rebuilt. i did add some new seals and LSD to it back in 09.

Mrmerlin

was something else done to reduce noise and now your hearing a new noise?
Was the old noise masking the noise you now hear?

Ladybug83

Could the new cooling lines be vibrating against something while under load? Maybe vibrating less when not under load

Ducman82

its not a vibration. new lines dont move.
I re did the rear main seal a month or two ago, but the noise did not happen till just last week or so. its very odd that it makes noise due to road conditions. I'm going to check wheel bearings for giggles today. they only have about 5k on them.

thanks for the tips guys.

Mrmerlin

check the axle nut torque and CV joints

dr bob

Considering the relatively recent LSD installation: Ring & Pinion noise, usually a whine when under load. In most cases there's a difference in the noise characteristic between leading and trailing throttle. If the noise changes or disappears when load is removed (clutch in or gearbox in neutral) I'd start looking at that. Remember also thatt R&P pitch changes with road speed, bearing noise pitch generally stays the same but changes amplitude with speed. If the noise you hear changes with road speed without regard to engine speed, you can narrow your search to the area between the pinion shaft (and fifth gear...) to the wheels; noises that change with the gear you are in will be 'upstream' of the pinion shaft and a gear set.

With car on lift and in gear, perhaps with rear tires removed, add some load with a helper with foot on the brakes lightly while you listen.

Ducman82

so a little more testing on the way to take the kiddo to Pre-K. cold, no noise at all. on the way home (warmed up) it would make the "rattle" ever so slightly. Then when pulling away from the housing gate (military housing), on a slight hill, it seemed to really make the rattle. so, I'm willing to bet clutch issue of some kind (sigh). how does one tell if the pilot bearing is going out, vs the throw out?