Aligning driveshaft with new used rear end ?

[Eighty8LX50]

I recently changed my rear axle out for a used one due to the original axle having a bad bearing. I now get a slight drivline vibration on the freeway that was not there before the swap, and I am thinking its because the driveshaft is not bolted in the right spot on the rear axle. How can I tell what the right spot for the driveshaft is ? Or do I just have to turn it until I get no vibration ?

 

[Scott_B]

just flip it over 180. Should get rid of the vibration.

 

[Eighty8LX50]

Ok, I think that means to go turn it basically oppisite of what I have it now ? I dont know what 180 would be

 

[gt90stang]

This may help:

http://home.hiwaay.net/~ctfrench/Driveline Vibration.htm

Good Luck, Don

 

[Scott_B]

Yeah, flip it 180deg. It can only go one way or the other.

 

[Eighty8LX50]

I moved it like said, and its exactly the same I get the vibe in 4 th - 5th gear range.I can feel it in neutral while coasting through the shifter nob. I have another drive shaft that came with this rear end, I think I should try that d/s with some new u joints.

 

[gt90stang]

Each DS and diff is matched at the factory. You can actually index the DS in 45* increments, you may have the clean out the threads on the previously unused holes.

Good Luck, Don

 

[Scott_B]

How can you rotate it 45*? Im pretty sure the bolt holes will only line up one way.

 

[gt90stang]

On my 90 there are 8 threaded holes.

Don

 

[Eighty8LX50]

Ya I think I have the 8 threaded holes, So your saying to move it up one by one hole at a time until I get the vibration out ?

 

[Scott_B]

Weird, i must be looking at the wrong thing..

 

[gt90stang]

Yeah, but I'd do 90* increments to find the best place then do +/- 45* to find the best. You can also do the front to really get it dialed in. I put mine on jackstands and BLOCKED the front tires front and back. You'll need a 12pt 12mm socket for final torquing and I used a box end wrench with an extension bar to break them loose. You can torque them down by hand for the short testing session on the jackstands. Once you get it dialed in use blue locktite and torque them to spec. You may need a 12mm x 1.75 tap to clean up the unused holes, I did.

I ended up with a hose clamp on the pinion flange to offset my 0.002" of runout. My vibration is now liveable but not totally gone. I have two vibrations with my aluminum DS 52 MPH and 63 MPH. I want to find someone who can field balance the DS on the vehicle.

Good Luck, Don

 

[HISSIN50]

Don, nice info.
IMHO, you hit the nail on the head - the best way to get rid of it is to have a driveline shop dynamically balance the shaft (while it is in the car - so the entire rotating assembly is balanced).
good luck.