AU xr6 diff into AU2 futura - help!

[blueoval]

HI guys, sorry for posting this in the wrong section but I kinda need some answers as soon as possible.

AU xr6 diff live axle, non IRS. 3.45 gears. LSD

I got my AU xr6 diff fitted last night, got everything swapped over ok.

I took the car for a test drive and noticed a rather heavy vibration which sounds like its coming from the diff. The vibration occurs mainly when not under load and slowing down. Under load its still there but less noticeable.
I know when my mate put the diff in, he checked both axles to see if they were bent which the werent.

We rang up a few people about this, and was told that this vibration could be the fact that I have re-used the futura trailing arms, and not used the xr6 ones. It was mentioned that the xr6's had a different geometry as they sat lower as opposed to the futura geometry which sits higher. (ride height Im talking about)

So if I was to get the xr6 trailing arms fitted, do you think this will fix my vibration issue?