jwbbuck

I've got a major noise / vibration only at highway speeds (4th, 5th or 6th) and only when at very light throttle settings. WOT or closed throttle and the noise goes away. Should I be looking at driveshaft balance or do I need to pull the tranny apart?

snake charmer

iTrader: (118)

I wouldnot go off tearing in the tranny at first . At lower rpms at those speeds the car will make vibrations at lower rpms jsut from an assorment of vibrations .
Is there any other symptoms ?
If it is working wide throttle or closed I am sure it is something simple or just loose somewhere and is not hurting you .

jwbbuck

I dont' have any other symptoms, but I've only got 40 miles on the car after a complete drivetrain swap. I"ll do a bolt check tonight.

Is there any way to check the tailshaft bearing without disassembling the tranny?

blk00ss

iTrader: (66)

What kind of tranny mount are you running? Stock or poly?

jwbbuck

Poly. 4 degree U-joint articulation back and front. I'm shimming both front and rear to 2degrees.

fbodyforever

iTrader: (10)

is it kind of a metallic rattle noise? there are quite a few people with the same noise, most in cars with higher mileage. i was told in posts on three separate forums that GM had an issue with throwout bearings making noise, at least on the LT1 cars anyway, it's not a "problem," but if it is changed out with an aftermarket one the noise will go away. i get it alot at part throttle under load at low revs. of course yours could be a different noise, i'd have to hear it for myself to say it's the same one i've got.

Wayne

jwbbuck

It's not the typical metallic noise that seems to be pretty common with T56's. Many refer to that noise as gear rattle and I have some during light throttle settings. The noise / vibration is much lower in tone and greater in amplitude. It may just be a driveshaft out of balance, but I wouldn't have thought that a driveshaft balance problem could be turned on-off with throttle setting changes. However, it is only an issue at certain vehicle speeds and occurs in any gear about 40mph.

I have the driveshaft from my donor car with a damper on the slip yoke. I may get it cut to length and balanced and try that one.

Travose21

iTrader: (22)

mine do the same thing when i am at a dead stop and off the clutch but when i put my foot on the clutch it goes away. and when i turn a corner and i am off the clutch it get louder and when i put my foot on the clutch it goes away. what could that be. I just put a 12 bolt in it like about 300 miles ago. changed the rear u joints and have a poly t-mount