Advice sought for final drive issues on 620 diesel

[JohnMacD]

I have a Rover 620 diesel.

I was under the car pulling at the suspension trying to locate the source of an occasional bonk-bonk sound (going straight ahead over uneven road), a clicktery click sound turning right on full lock (been there for many years and doesn’t seem to get worse) and a little clutch judder when starting off from stop. I couldn't detect any problems in the suspension but noted the following.

The nearside outer CV joint can rotate across the joint, i.e. lost motion in the shaft, of about 0.5 deg. The inboard CV joint itself seems fine. All gaiters are intact. However, the drive shaft input to the gearbox can rotate with respect to the gearbox about an axis at right angles to shaft through an angle of some 1.5 – 2.0 degs, i.e. it flops about inside the gear box. I don’t detect any lateral movement of the gearbox side of the drive shaft when I try to move it with respect to the gearbox, only angular.

The outer CV joint probably needs replaced. Is it likely the splines on inboard CV joint are the source of the floppyness in the gearbox and they have been damaged? Can anyone recommend the best source a replacement for the outer CV joint or should I be trying to pick up a complete second hand outer drive shaft?

I bought a new gearbox on ebay some time back in case I needed a spare so it could be time to fit it. I read MattyPrice4004’s excellent article on replacing the gearbox. I am thinking of replacing the differential bearings with steel caged ones but am concerned about messing up what should be a very serviceable gearbox. How hardis it to replace the diff bearings. Should I replace the outer bearings with non plastic cage ones or should I just accept that I have 132K on the clock and the plastic cage bearings will outlast the car? Can anyone recommend a good source for replacement diff bearings?