not knowing much about the F2, I defer to
@Nodge68
The FL2 uses a very similar system to the FL1.
The FL2 uses a PTU, which effectively does the same job as the IRD in the FL1. The only difference being the front diff, which is still in the gearbox of the FL2. The PTU takes power directly from the diff carrier, using a spline coupler tube, very similar to the spline link in the FL1 gearbox. The drive from the gearbox is then turned 90° by the PTU, so it can rotate the propshaft.
The FL2 spline coupler is known to fret and wear, which basically disconnects the drive from the gearbox to the PTU, meaning the PTU doesn't have any power to send down the propshaft to the Haldex.
The Haldex is basically an electronic version of the VCU, using a wet clutch pack, pump and piston, instead of plates and fluid.
The Haldex is switched in and out as needed.
The propshaft will still rotate with the wheels, as the diff will "back-feed" the drive from the wheels, through the Haldex (there's always a slight drag on the plates), which is enough to turn the propshaft, giving the impression that all is well, but that can't be guaranteed without some proper testing.
My own FL2 has had at least one replacement rear diff, shortly before I got it, which then seized, so I've now rebuilt another, which is all good so far. My FL2 also has a clean looking PTU (much cleaner than the gearbox it's bolted to), so I'm thinking my PTU is also a replacement unit.
From doing lots of reading and research, I'm not convinced that the FL2 drive train is any more robust than the FL1 drive train.
