Not wishing to Hijack this thread but it is related to Audi boxes and BUDGET,
Audi modified the 01E at least 4 times in its lifetime to make it last longer, bearing carriers plus 2 of the more famous upgrades were wider first gear, but I believe the last was modding the spigot shaft so it acted like a torsion bar and absorbed some initial clutch dump shock.
As far as I am aware they didn't mod the diff.
Is this the right place to look for failure or is the damage just the symptom of a weakness somewhere else?
Mixing and matching parts, plus reading the above sounds like quite of bit of work if your paying for it by the hour, plus if one it lets go you could total the box! Are you starting with the right box? How much will this cost?
Some time ago I had a job lot of top spec 01E Audi boxes, I advertised them on here, I didnt have one enquirey, I sold one previously to a GT40 builder (manufacturer), ones headed for a Lambo + chevy combo the other to another mid engine chevy setup. Couldnt shift them for £1500 brand new, strongest variation of the Audi box, good for 400bhp according to Audi themselves, but would expect them to sustain more as they were the top spec.
I am sort of with Ross on this, your building a sports car with a big V8 in it, do you really want to spend all your driving time nursing it along in the hope it dont go bang
Sooner or later someone in a Nissan Skyline or such like will be parked right next to you at lights, or tagging you at a track day. If this isnt the time to flex the V8 then why build a GT40?