Apikol Rear Diff Mount
 

So, I fitted a new Apikol main rear diff mount today.

It's a job I've been meaning to get to for months, ever since my off-throttle to on-throttle jerking and 4th gear thumping started back up again after a bad incident involving a bad 1st-2nd shift when my MAF failed.

It's not too bad a job. Remove the rear exhaust section and loosen the heat shielding forward of the diff and you give yourself all the required access. A transmission jack was handy to support the exhaust during removal, and the diff with the mount removed.

The standard mount has a 10mm hole through the centre bush. The Apikol Mount has a 12mm hole (actually pretty certain it was ½"). Not sure why they've done this, but it actually turned out the be fortuitous.
The old mount was actually OK, but the mounting bracket on the chassis had been flogged out a bit. The bolt and nut had loosened slightly over time and were allowing movement of the diff. Tightening of the bolt would only be a temporary cure, as it would be purely a friction hold with a little bit too much allowable movement in the bracket.
There was limited room to work, but we fitted a 12mm tear drop burr into my mates air drill and ground out the bracket (and the handbrake mounting clip) to 12mm.
A visit to the bolt shop later and we bolt the Apikol mount into the bracket with a couple of good fitting washers (good size guess with mudguard washers that were a beautiful neat fit into the bracket).

Tighten everything down bloody tight with 2' bars, and everything was reassembled.

Final verdict:
Drives beautiful again! Smooth shifts, no jerkiness...
It's nice and tight the way we've mounted it.
Anyone else considering the Apikol mount, just be aware of the ½" hole through the mount. If your bracket holes aren't flogged out like mine were, you might want to find a lathe and a bit of aluminium and turn up a ½" to 10mm reduction bush. Also replace the cone-lock nut on the original bolt (assuming mine was original). Nylock will do at a pinch, but a cone-lock is best.

Sorry, I didn't document in photos... This is the only one I took!
http://forum.a8parts.co.uk/attachmen...4&d=1519305021

Interesting. Is that a C5 part or specific for the D2? The diff is the same but not sure about the mounts.

I bought it directly off Apikol using the navigation to the A8.
I just looked up C5 A6 to see and they do look very similar. There's no cross reference on their site though, so we'd have to check ETKA.

I did buy the rear mount bushes for the C5 though, as the genuine ones are the same part number. The factory ones are a bonded metal-rubber bush, while the Apikol urethane ones are a two piece and shouldered bush with a metal inner sleeve. The C5 rear mount must be slightly narrower as the bushes are just a little shallow in the neck for the D2, which we were going to fix in the lathe after freezing them.
However the rear bushes on the car were in excellent shape with very little movement, so we left them alone.

Besides, took us half a day by the time we stuffed around going to the bolt shop and having our roast pork rolls for lunch!

Ok.
Part numbers are different.
4B3599125 vs 4D0599125D/E

The Aluminium housing looks quite different, mainly around the three mounting holes for the diff - despite the bolt holes having to be in the same place if the diffs are the same...
The rubber bush is slightly different too (elongated centre metal shaft, versus the round shaft in the mount I pulled off the car - which was replaced previously so can't guarantee its genuine).
Uses the same 10mm x 85mm bolt to mount through the bush too...

Whether the main bush is located differently is the only thing that could be different I suppose...