captainOCD

The other night I pulled the car out of the garage, got partway down the street, and started hearing what I'd describe as a loud whirring/gear mesh sound coming from somewhere in the center towards the firewall. It only seemed to do it under light load and only while moving and in gear. Since I was going somewhere I put the car back in the garage and came back to it today.

I drove the car around the street a couple times and maybe once could hear the noise, but nowhere near as loud. Drove the car a couple miles around town and still nothing. All I can hear from underneath is a very very faint whirr that I'm guessing is coming from the torque tube. This has been present since I got the car. Only having had the car for 6 months or so and putting maybe 500 miles on it or not, I don't know if that faint noise is normal or not.

So I've been reading up on torque tube and converter bearings. I couldn't really find any videos showing a 928 driving with torque tube noise, closest I found was a 944 and it really didn't sound like what I heard the other day. The constant whirr I've had the whole time with the car got me wondering if it's normal or not though. I've read that due to the design of the clamps on the driveshaft, it could be pressing on the flexplate. This thread mentions noise going away when releasing tension from the driveshaft clamps: https://rennlist.com/forums/928-foru...xperience.html.

Is releasing the tension on those as simple as loosening the bolts then retightening them or is there more to it? I found lots of mention of checking them, but not anything saying exactly how to do it. Maybe I'll get lucky and this will be the cause of my noise the other night.

Mrmerlin

Hi Matt Thanks for the update.

I am guessing you have a auto.
Since your asking about checking the pinch bolts,
it would be wise to do a crank end play check and remove and inspect the front and rear pinch bolts.
NOTE install the rear pinch bolt first torque to 66 ft/lbs add a drop of blue thread locker top the bolt threads
after this is done then you will begin diagnosing the TT and TC bearings

captainOCD

Yep it's an auto (which roger tells me is the best). Thanks for the info. Hopefully tomorrow I can check the end play and check if there was any tension on the flex plate.

dr bob

Matt--

While you have the car elevated for the endplay testing and such, consider taling some minutes at the end of that to start the engine and crawl back underneath to listen for the offending noises. A mechanic's stethoscope is a handy tool for finding sources of noises. Absent tht you can use a screwdriver stuck to your ear, but in this case the stethoscope is a LOT easier. With engine running the driveshaft spins in the tube at engine speed. Place the probe to the tube in a few places along its length, and to the nose to the TC housing where the bearings live. Use the sounds and location to decide the sources. Then decide a plan of attack.

captainOCD

I have stethoscope and chassis ears if need be.

the flyin' scotsman

the drive train can be isolated from the engine by loosening both bolts on the front flex plate and TT shaft clamp then pushing the clamp to the rear until its clear the flex plate effectively disconnecting the engine from drivetrain. Start the engine and listen if the noise has been eliminated, if so you verified its downstream of the engine. Shut the engine off reconnect the clamp and follow the direction by doc Bob above.........good luck.

captainOCD

I'll keep that in mind too.

DonaldBuswell

Stan, over 22 thousand posts...really? Wow...

captainOCD

Well I'm out in the garage now. When I loosened the front clamp bolt I got 3mm of movement. The flex plate was bowed enough that it was pushed into the flywheel along its inner diameter.

captainOCD

And using my dial indicator I measured 6 thousanths of an inch endplay which I believe translates to .152mm in metric. According to the spec of .11mm and .31mm for factory in Dwayne's thread, I think I'm in good shape there.

FredR

That is a commonly found amount of slippage not that it is acceptable.

That crank end float is excellent - this is something you needed to know.

captainOCD

Looks like I snuck that in right ahead of you.

FredR

You certainly did but I was quicker on the redraw!

captainOCD

Yup.

And I must just have small hands. I managed to get all 6 flywheel cover bolts out without lettingl the exhaust. Now whether I can pull that off with the heat shields over the back is yet to be determined.

captainOCD

I managed to get the heat shields away from the access point for the rear clamp bolt without having to drop the exhaust. It sure wasn't loose to begin with, but it's got some fresh loctite on it now. Got everything put back together and took the car for a ride around the block. Didn't hear any sign of that noise I heard last week. Still have that very faint whirr and it seems to be coming from the rear of the car. I'll have to poke around with a stethoscope at some point.