Just because your driveshaft is new doesn't mean it's not crap. Do what I suggested then we'll know. I know some guys who built a GT350R clone for a guy, came back a week later, bad vibration. We could see floor jack cleat marks in the driveshaft. Wasn't like that on the test drive when he picked it up and drove it home. Swore he didn't do it. Yeah, right, you think his teenage kid would admit doing it? Musta been gremlins.

 

Reading this brought some memories of mine trying to track down a bad vibe.

I know this sounds to simple to be true but it was the reason mine was shaking so bad.
Did you have the matching U-joint for your rear end yolk put on your drive shaft then have it balanced?

I wound up with a 9" before off who knows what and the ujoint was the wrong size just by a tiny bit and once it rotated it shook actualy moved int the cups b/c it wasnt wide enough.

That issue was solved with the new Currie center chunk and 1330s.
Its worth checking at any rate.

 

I'm not that advanced in this matter but if you run the engine while you have the trans out then you might know for sure if it's coming from the engine or further back.

 

Now that brings back memories. A junkyard I used to go to (huge place in NJ) would run engines if you wanted to hear them. Laying on the ground, in the storage building. Always looked weird to see an engine running with no car.

 

I don't know what your issue is but this stuff sure sounds familar to me. When I bought my 69 coupe with a 390 and C6 it had a really bad vibration that was worst at freeway speeds. THought for sure it was tranny related but went to a good transmission shop and the owner had their top guy test ride in the car with me. After running thru several of the tests that have been mentioned here, the guy tells me to head back to the shop. Proceeds to tell me it is driveshaft and not transmission. I was ready to spend several hundred on a rebuild of my tranny and all it ended up costing me was about $120 for a driveshaft tumble clean, spin balance and installation of new (american made) u-joints. After that, the vibration was gone. I was very impressed with the tranny shop who could have done the tranny work but was honest and saved me a ton of money.

Might be worth taking your car to an experienced tranny shop and let them test ride in the car with you if you haven't already.

 

You all have valid points and comments. I did not run it without the trans in. I was lazy and it would have solved a lot of back and forth.

I had a 92lx drive shafted taken apart and retubed. It was done by Phoenix Rack and Axel. They are great and they balanced it with the yolk and the pinion flang on it to 10,000 rpm's. I asked if it ws truly 10k rpm's and the dude procedded to show me the machine. And holy shat! it was true. And balanced perfectly. I then went home and installed. it.

Next monday i am going to install a fresh T5 and i will see if that solves this issue. I am sure it will.

 

whats the tag number on the t5 you have in there now?

-Gun

 

CRAP I WILL HAVE TO GET UNDER THERE AND FIND OUT. i WILL DO IT TOMORROW. i LEFT THE CAR AT MY SHOP