Exhaust Vibration

[Au2falcons]

Hi Guys,

Hoping somebody can offer some advice.

The exhaust in my AU is vibrating in drive/reverse only.

Base idle appears ok.

The car has IRS so the pipe runs under the diff, there are four mounts in total. 1@Transmission, 1@front of Diff assembly, 1@rear of Diff assembly, 1@tailpipe near tip.

I originally had no vibration, but recently noticed that the rear 3 mounts were heavily cracked so i've replaced them with genuine items. Now I get the vibrations.

I have looked under the car whilst it is vibrating and the pipe directly under the diff is bouncing up and down about 10mm. It does not touch the diff assembly, but the movement is sending the vibration through the mounts and into the chassis. In front of the diff, and behind the diff the pipe is steady, it's just this small length that is bouncing. Engine is steady, could balance a 50c piece on it

Any suggestions?