I believe your car has a t56 transmission, correct? If so, there is a bushing in the extension housing that keeps the clearance between the yoke and the extension housing tight to keep the yoke straight and concentric around the tranny output shaft. Now excess clearance between the yoke and bushing will allow vibration to occur. If you have a problem with the clearance that is causing the vibration, it can be due to either a worn bushing, a worn yoke, or both. So there are a few possibilities that would cause you to have the vibration after switching the transmission and/or drivershaft. Most likely, both the yoke and the bushing on your original equipment are worn. If so, then you would still experience a vibration by swapping the tranny and using your original driveshaft due to the worn yoke. If the ebay tranny didn't have the bushing replaced (which I wouldn't know), then the worn yoke would be compounded by a potentially worn bushing. Now to the swapping of the 01 aluminum driveshaft...If you swapped the 01 driveshaft into your original tranny, then you would likely still experience a vibration due to the worn bushing in your tranny, but it would likely be decreased because though the bushing is worn, the clearance between the "newer" yoke and the bushing would be tighter than that of your steel driveshaft's worn yoke. This is consistent with your post above indicating the vibration decreased when you swapped the driveshaft. Have you tried the 01 driveshaft with the ebay tranny? In theory, this would be the best combination to determine if this is your issue. I hope this helps.

Yes I did. I had the ebay trans in with 2 diff driveshaft... the last thing I did was swap back to the OE trans.

does anyone have a write up on doing the tailshaft bushing in the transmission in the car?

was this car ever in an accident ?

nope

do you have a poly trans mount and rubber engine mounts? If so, change the poly mount to a rubber one.

t56 trans' are very sensitive to output shaft harmonics, and in some cases have problems with looseness in the 5-6 cluster extension(should be pressed on and off, sometimes they are not that tight and cause weird vibrations)

my brother had a weird resonance/vibration occurring in his car due to the mismatched engine mounts. once we put the rubber mount in the car, the vibrations went away.

I just ordered a rubber mount frm the zone... I have a poly trans mount and rubber engine mounts. Im going to try it... for $15 why not

sorry if this is a repost i didnt feel like reading all of this thread lol but did you try setting it at different pinion angles?

it was at like -6 before i set it to -2.. didnt change it at all

Did you do the tail shaft bushing yet?

No sir. Apparently it has to be done with the transmission out of the car... Im going to throw in a rubber trans mount for kicks and giggles... if that doesnt do it then im just going to send the transmission to tick. IDK what I will do with the ebay transmisison, maybe try to fix it myself.

Call Bob Hanlon!

details :O

See Hanlon Motorsports in the sponsor list on the right ------->

- Justin

I put the rubber trans mount in... made no difference, now the vibration is even worse... it starts at ****ing 40mph. i want to kill myself. the weather is beautiful and my car is on ****ing jackstands in my driveway. if anyone wants to stop by and maybe look at it while I drive it on jack stands or something. HELP

Tail shaft bushing still not replaced?

- Justin

I was told it has to be done out of the car... I just think its odd how 2 transmissions could have the same issue. I guess ill just drop the trans lol

Is the tail of the T-56 removable like a 4L60e is? If so, just pull that off and leave the trans in place. Should be able to get it done that way.

- Justin

The tailshaft has to be removed outside of the car. you can take it off in the car but cannot put it back in. I am tempted to bring my ebay trans to hanlon and have them look at it. see if anything is bad... and if nothing is bad...... then.... i guess i need a rear lol

anything ever come of this? the new, well "new to me" 98 z28 t56 has a vibration starting about 60-65 and gets bad about 70-80. it evens out some above that but is still bad. driving around up to those speeds has no vibration. 2 different sets of wheels no change. guess ill have to start checking some of these things. my car is not worst with the clutch in. anyone have a cheap drive shaft for sale?

I have a stock steel drive-shaft if you want to pick it up $40.00

Location Staten island, ny

thx but after gas and tolls ill be over a 100 lol

You ever get that vibration fixed?

Update. Swapped the rear. issue still there. I am going to look into the complete driveline angle (including trans, not just the rear). I set the rear pinion angle to -1 but didnt account for the trans...

Great info on LS1tech

http://ls1tech.com/forums/lt1-lt4-mo...r-ls1tech.html

NOPE. still there! swapped rears, transmissions, driveshafts, everything...

surprised you remembered :) I am thinking its the whole angle of my transmission and rear. I never measured my transmission angle.

Lots of great reads on my recent LS1 tech thread

http://ls1tech.com/forums/lt1-lt4-mo...r-ls1tech.html

Very few from the Flemington area here, so yeah, I remember you!

Def. check the pinion angle w/ that adjustable TA.