Aristides, lots to discuss there…because this is a modified car, we have modified car problems.
The stock driveshaft is long gone, replaced with a 1 piece unit that is either 3" or 3.5" in diameter, much bigger than stock.
We’re applying a LOT of torque to the differential (estimating 450 ft-lbs) so it’s not really surprising that the cage is moving. The mounts are not delaminating, they’re just moving because they are not designed to resist motion in that direction. Furthermore, the yellow bumpers are softer than I anticipated, combined with some bending of the traction bars, so the movement is not as limited as I’d like.
Combine a physically large driveshaft with lots of torque and it’s bound to kiss the tunnel. The gap is small to begin with, maybe 1/2".
I think the XJS owner is Rob Wade, I recall seeing some posts by him here. He had some sort of structure built to resist movement. Good info here:
The trailing arm bushings may have helped a bit but are designed to be compliant and squishy for comfort. They also only restrict movement in the fore/aft direction, not in the up/down direction. I installed the big bushing with the voids in line with the trailing arm (parallel).
More to come! I am excited to try the new traction bar setup out, just need to make time in the garage.