Issue: There is a fairly loud rattle coming from beneath the car. Gets more pronounced when the car is warmed up and hot. From underneath and with a screwdriver to my ear it seems to be coming from where the trans meets the TT; or more accurately right on the TT where the tube meets the bellhousing.This seems to point to the rear TT bearing except I get ZERO vibrations (except the lope at idle which seems is normal per online forums) anywhere in the RPM range. The only symptom seems to be the sound. Ive read every single article and post I could find on the subject and it seems usually TT bearing issues manifests as a vibration. Could the bearings be bad and not cause ANY driveline vibrations? I mean its moderately loud. My Vette sounds like its got a tiny diesel engine somewhere in the middle of it.

Ive also considered the exhaust touching somewhere being the cause ( the h pipe flange is in fact VERY close to the tunnel shield up front) but the sound so clearly comes the previous mentioned spot that I seriously doubt it.

Also there is very little mention about a problem with the "driveline support" nut coming loose and just needing to be retorqued. I believe it was even a tsb about it. Yet I can find next to nothing about it anywhere except one guy (I believe on this forum) mentioned it only vaguely; paraphrasing "Yeah had that noise to, took it to the dealer and they fixed it, said it was bracket in the torque that was loose and needed to tightened." Other then that I cant find anything else about it. A thousand pics and articles about torque tubes, bearings, bent prop shafts,quibos ect but nothing about a "driveline support" nut; which supposedly is what GM calls it. Any thoughts? Or even more helpful would be actual personal experience.

PS I understand all the ins and outs of the common TT issues and what it takes to repair it so im all caught up on all that. Just interested in information to help properly diagnose it. Thanks in advance

 

"Driveline support" is GM's term for the entire torque tube assembly.

It sounds like the guy is referring to the clamp that attaches the crankshaft to the driveshaft inside the bell housing. It's only present on automatic cars.

 

Ive read about that issue before but have always discounted it as the source because the sound appears to be coming from the rear. But I guess i should check it if only to eliminate it as the sound. When I pull that little cover am I checking for the whole clamp to be loose or the bolt or both?

Can you have bad TT bearing yet still have no driveline vibrations, just a sound?

 

The bolt tightens the clamp around the splined socket on the back of the crank, securing the driveshaft inside it. None of the above should be loose.
I would think so. You can have a noisy wheel bearing with no apparent wheel imbalance.

I have taken my (manual) torque tube apart so I'm familiar with the insides, but mine didn't happen to be noisy.

 

I had a bad drive shaft bearing with no vibrations.Bad rattle in park could not hear it while driving driving because of loud exhaust.

 

Exactly my symptoms. Well hopefully it wont get too bad between now and early next year. Ill be getting a 2nd vehicle hopefully then I can remove and rebuild the TT at my leisure. I have considered a Carbon Fiber prop shaft (with new bearings) and eliminating the guibos, but im worried about the vibration caused by runout that some guys have reported. I have read here in old threads the CF shafts are perfectly balanced but need to be machined with the input shaft mounted to eliminate runout. Any new opinions or findings on the topic?

 

When mine went out, it was the front, but sounded like it was the rear, I think it was the way the sound traveled. Also in neutral, if I revved it a bit and held it, the noise would go away.