F23 requires gearbox removal and the box stripping down.
I have decided to replace the bearings on the new diff with Timken (steel cage) bearings, they were the plastic cage type and were a little noisy when I span the diff in the housing.
The guy I bought the diff from said in his experience it does not matter which bearings are used or whether the uprated end casing is fitted, it's how much oil you put in the gearbox which matters the most. He recommended 3.5 litres, standard is 2.4 litres. I am going to put in 3 litres of the Dexler LSD oil instead of 2.4 litres of the standard gear oil which I have been using.
He did say that when the plastic cage bearings fail they tend to cause damage to the gearbox, whereas the steel cage just make lots of noise.
All he does is rebuild M32 gearboxes and he had several hundred gearboxes in his workshop.
I have pulled the old bearings off the diff, just ordered some bearings, so the rebuild will have to wait.