[Mostly Thumbs]

I just replaced the center support bearing it was a pretty easy job. The bolts holding the two parts together were kinda stiff and I had to drop my exhaust(that was hard because the morons who put it on used sh*tty bolts and they were very hard to remove). Anyway after I replaced it the clunking driveshaft noise is gone, thank god, but there is a vibration that seems to come at a 3000 RPM in the 1st, 2nd and 3rd and then go away at higher RPM. Is this caused by a out of balance driveshaft or something else? I think the car has a lot of miles on the woreout bearing, could this have caused it? Thanks for any help.

 

[drjonez]

i'd guess you didn't light up the 2 pieces of the DS correctly when you reassembled....

 

[51Cards]

Interesting that the vibration appears at the same RPM in each gear. The D/S would be spinning at different speeds in each gear at 3000rpm so you'd expect the harmonic vibration to occur at different RPMs. If it's the only thing you touched though it would be the first place to look.

 

[SupraMK3]

I agree with Dr. J... if you seperated the 2 DS pieces, and then reconnected them the balance of the driveshaft could have gotten thrown off. You might have to remove the whole piece and have it rebalanced.

 

[Mostly Thumbs]

When I removed it I marked the flange so it went back together the same way it came out. Could it be exhaust related? Since it seems to be at the same RPM and I did drop my exhaust, if the cat back wasn't connect firmly to the cat might htat cause the problem?

 

[51Cards]

I guess it would depend on whether you're feeling the vibration in the body of the car (D/S) or you're just hearing something vibrating against the body... (exhaust)

 

[Mostly Thumbs]

It's not a real strong vibration, but definately noticable.....I'm goning to go check the exhaust flanges etc. I hope that is all it is.

 

[LJM61]

Hi MT!

I have the exact problem in my 88T.
Just after I first got her I started to notice the vibration between 2800 to 3200 rpm's but only in 3rd gear, but not at all either below or above that rev. It wasn't too bad, but noticable. Over time I started to feel it more and then I could start to feel it in 2rd and 4th in the exact same rpm range.

I finally took it to my mechanic to try to find it.
I know it wasn't engine(Just had it rebuild after a BHG-also the reason I didn't look into it sooner) and we eliminated it by trying different tests. We finally focused on the half shafts and drive shaft.

We put the car on a hoist(resting on the chassis-free wheeling) and I sat in her and went threw the gears up to 4500rpms. Free reveing out of gear didn't produce it, bit in gear it was even more pronounced with the wheels floating in space. We took off one wheel on the side it felt strongest(rear drivers side) and when rotating slowly, the rear half shaft was not turning in perfect orbit. It was definitely slightly warped. The other side was fine.
So we replaced the driver side half shaft and it was much better. Better but not perfect. Now we're looking at the drive shaft. There was a lot of play in the damper in the middle joint.

I haven't had the chance to follow through and replace the damper first and if that does't cure it. Replacing the drive shaft is my next move.

P.S.>>>
check the rotation of your half shafts as we did and then check your mid drive shaft damper to see how much play you have in it.
Buying a used drive shaft from a wreckers is a crap shoot. see if they can varify or guaranty that it's also not bent or out of round.

P.P.S.>>>
I'll start another thread on this when I get a chance to replace my damper. Let us know what your going to do.

 

[Mostly Thumbs]

Well I checked the bolts on the exhaust (cat to catback and one of the crappy bolts they had used was sheared. So I limped down to Canadian Tire and replaced both crappy bolts with nice new shiny ones. The problem is WAY better now but still there. It seems to be mostly at around 50kph, but is much more pronounced in 2nd and 3rd gear. In 5th at 50kph I can't feel anything. I took it up to about 80 and it actually seemed better in 4th. I have to drive into work tonight so I will get a chance to try some higher speeds.

LJM61- That is a good possibility about the shaft being warped. The bearing has been bad for quite some time (since I've owned it 7500km ago and who knows how long before that). I would imagine that long term bouncing on a bad bearing might give it a little warp.

Final question, what can I damage driving it like this ?

 

[Mostly Thumbs]

Fixed...ish

I was talking to a local GM guy and he told me that a quick way to balance the driveshaft was to use hose clamps as counterweights! Sure enough I put two hose clamps on the shaft and the vibration is almost gone. I think I might need a little more weight in the same location so I was going to put another clamp but the heavy side of the clamps (the screws) is exactly opposite a small counter weight on the other side of the shaft. So I was thinking of just busting that off and using one clamp for fine balancing. Any input on this?