I've had a little project on the go for a bit. Not my car but the basics are late bf sedan fg turbo engine, bf f6 pcm and ZF6 and a few other bits and pieces.
A couple of shops here in Perth (not xft or monsta torque) have had the car and haven't been able to sort it.
I found a heap of config issues between the ic/pcm/abs and tcm. I've worked through those but still had an issue with the car grabbing neutral on the 2/3 shifts under load. I was about to condemn the trans but noticed some weirdness in the logs from the abs unit and tcm.
In the course of testing it broke the lh inner stub axle (no skids not my car) do after searching around u found a complete bf f6 rear cradle with repco shafts and sp diff bushes from a local wrecker.
The owner managed to grab this for a song so with the help of my Son, my Dad, Turbo Knapp and his rodeo and eventually even the wife we got it from its resting place in the front packing Bay around the back and on the hoist.
I then set about removing the rear end and too my surprise found the rear end the owner had paid one of the shops to install to suits the xf was actually a 4 spd open centre 3.43 The tcm ans pcm and even abs and David calibrations are all set up for a 2.73 lsd rear end! I'm pretty convinced there lies the issue. I believe the pcm and tcm are seeing an engine rpm, trans out put and wheel speed relationship that does correspond with the values allowed for the 2.73 rear and this is upsetting the whole deal
Tl:dr
Pulled a diff out and it's was diff(badoomtish)erent to what it should have been.
Pics-
Old rear end comes out
New rear end goes in-