HELP! Diagnose drivetrain noise?

[hemibeep]

So I am driving the car normal in traffic. I hear a sound like something is wrapped around driveshaft and hits metal.....thawp....thawp...thawp.

1. This sound is only under load - it goes away if you depress the clutch while at speed.
2. may speed up at higher speeds -don't recall.
3. car on lift shows nothing loose
4. recent tranny mount, which is still okay.
5. no obvious signs of any rubbing or interference in or around the rear.
6. nothing appears damaged or broken.

Wheel bearing?
u-joints?
half-shafts?
sound goes away under coast.

thanks

 

[RobZilla]

If it goes away under coast it's most likely gonna be something in the bell housing where the clutch assembly is. You're probably gonna have to get in there and take it apart to find something.

 

[hemibeep]

clutch and throw-out bearing under 3k miles. LUK brand....
I don't know how to replicate the noise with the car on the lift to find the source.?????

 

[CROM]

Did you take the flywheel cover off to see if anything falls out?

 

[99 R/T 10]

Yep, start with the flywheel cover, but it sounds like you might have lost a couple of bolts off of the flywheel or clutch assembly.

 

[hemibeep]

Pulled the flywheel cover, NADA....
one full revolution, nothing loose, of course not able to check the flywheel to crank bolts. Hard to imagine these as an issue, as they were replaced new with clutch replacement (factory locktite).

I just do not see and loose or intereference within the drivetrain. what does rear wheel bearing sound like? Of course, the sound should remain in a coast as well.
thanks

 

[Tom F&L GoR]

During an autocross I ran over a cone and the thin aluminum clutch cover got dented and pushed on the back side of the flywheel. Has all the symptoms you describe. But you took the cover off and no scapes showing?

 

[hemibeep]

no scrapes, perhaps I should take the car off of the lift and drive without the cover? Just not big on driving with strange sounds coming from below.

Why does Tom Sessions have to be 600 miles away?

 

[johnk]

Rear end going away? Perhaps it only makes noise when there's a load on the ring and pinion or bearings, hense why it goes away with the clutch in or coasting.. It would be interesting to get the back tires off the ground and rotate them by hand to see what it feels like. Good luck,,,,,

 

[Venomiss]

no scrapes, perhaps I should take the car off of the lift and drive without the cover? Just not big on driving with strange sounds coming from below.

Why does Tom Sessions have to be 600 miles away?

Have you called him to see if he had any ideas for you?
Might be worth a phone call and he is a nice guy.

 

[Tom Sessions]

I think i would be looking at the rear end.If you have a broken tooth it may only make noise on accel or under load.While coasting you have now load on the ring and pinion and the noise goes away.Does it make a difference what gear you are in?does it make noise in fourth gear?If the noise is there in all gears its most likely not the trans.If the noise goes away in fourth gear than you may need to be looking at transmission problems. Call me friday afternoon and we can talk.910-228-8477.

Thanks Mary

 

[Venomiss]

I think i would be looking at the rear end.If you have a broken tooth it may only make noise on accel or under load.While coasting you have now load on the ring and pinion and the noise goes away.Does it make a difference what gear you are in?does it make noise in fourth gear?If the noise is there in all gears its most likely not the trans.If the noise goes away in fourth gear than you may need to be looking at transmission problems. Call me friday afternoon and we can talk.910-228-8477.

Thanks Mary

You are very welcome!

 

[hemibeep]

UPDATE:
Having an objective ear in the car, we have some different ideas.
-no sound present under accel.
-no sound until 3 or 4 th gear, Have not tried 5th or 6th
-sound starts under decel.
-really sounds like "slapping" of metal against tunnel ?
-tranny fluid good
-tranny mount good
-driveshaft and u-joints good.
-sound coming more from the rear, beyond the tranny, further back
-wheels up, rotate tires, cannot make the sound, either forward, reverse, fast stop...etc.
-really checked everything around for something loose that may be slapping around

any further ideas.?

 

[Tom Sessions]

remove the fill plug on the rear diff and stick a magnet into hole. try to get it all the way to the bottom and see what comes out.it sounds like a broken tooth on the ring and pinion