I just got a new aluminum driveshaft with new u-joints installed by Mazdatrix and my car had some time on the dyno and when I got it back I went on a test drive. Everything seemed good until I got on the freeway at about 65mph and the whole car started vibrating. (seems like it is coming from the rear). It is speed related not rpm. I pushed in the clutch on the freeway and it made no difference.

Checked oil in rear end and it was fine. Tires are new, but have 2 dyno sessions on them- could that have thrown them out of balance? The driverside halfshaft has some play in it, could that be it? Jacked car and pull and pushed on wheels and they have no play. Lug nuts are tight. I don't know what the problem is!!! Help!!

 

i had the same problem on mine when i would hit 65-75. there was too much play on the driveshaft. turned out to be the wrong driveshaft from a manual trans. when i had an automatic trans.

if it sounds like a wobbling noise near the transmission tunnel or the rear its the driveshaft. if its the steering wheel that shakes or the rear shakes/bounces/wobbles its a balancing issue.

how much play do you have on the halfshafts

 

The whole car just shakes. Like I have 2 15 inch woofers or somethin' but with out the sound of the bass, just the feel.

The driver side shaft has a very small amount of play. I searched and saw that this seems to be a common problem but I did not find anyone that was able to fix it.

I am getting my tires re-balanced tomorow to see if that is it and praying it works. I also searched aluminum driveshaft vibtation on google and it seems to be a common problem on all cars with aftermarket aluminum driveshafts so maybe it is just the way it is but I don't know. Everytime I fix something on this car another problem arises... ahhh!

 

Why did you need an aluminum drive shaft in the first place? Has it been balanced?

 

Check motor and trans mounts. If worn and drivetrain is slightly askew, vibration.

 

My old u-joints were shot and the stockers are unreplaceable so I needed a whole new shaft, It doesn't really matter why I needed it though.

Motor and trans mounts are brand new. We greased where the half shafts meet the rear end and got the tires balanced and a 4 wheel allignment and the vibration is almost gone. Thread can be considered closed. thank you to those that helped and no thanx to people tryin to start wars over if an aluminum driveshaft is needed.

 

My car has the same problem BUT it hasn't been aligned in 2 years and is probably on factory mounts/bushings still. its not in great shape but its a project so you know how it goes. you give me some hope that an alignment will fix it though,lol.

where did you get your aluminum driveshaft? know of anywhere that sells carbon drive shafts for the manual t2? my friend has a sileighty and he got a carbon shaft with it and it is so light! probably would lose a lot of rotating mass that way and make the car a little quicker,no? I don't know about strength vs stock shaft though. I'm aiming for around 300rwhp eventually.

 

try unbolting and rotating the u-joint 180 degrees and see if it changes the vibration at all, or just bring it back to them and tell them it is vibrating

 

i have a similar problem but at 100mph and its not as bad as urs sounds

 

helps if you say how you resolved it

 

It is getting better the more I drive it so I think it was my tires. It is like barely noticeable now. If it isn't completley gone soon we will rotate the shaft.