Slack in Diff
 

I have noticed a bit of a clunk as my 300D changes gears.

I recently bought new aftermarket (GSM) axles. Had to make a mod of the axle to hub sleeves/bolts because the aftermarket splines must have fitted differently. Thought clunk might have been these splines, so today checked the tension on the M8 hub bolts. But they checked out at 30NM torque and seemed fully inserted.

I jacked wheels fully off ground and rotated wheel back and forth. There is quite a bit of slack without the driveshaft moving.

Car has done 450k+ km. Is it normal for the diff to have that sort of lash (about 1 1/2- 2" at tire surface.)

For a more clear idea of what's going on, once the car is off the ground I would raise each sub-frame with small jacks, ie: scissors, to allow the axles to be horizontally level and then do your checks.

Would that be to check what part of slack may be in CV joints? Or is there another reason? When you say raise subframe, do you mean lower control arm?

The axles/CV joints are new annular and just installed. I did check that the flanges at the diff moved along with the wheel.

I do need to do a better check. Only spent a few minutes checking lash because I was more concerned about the axle bolts possibly having loosened up. (they hadn't) I didn't put new washers on the axle bolts, but will. FSM recommends that we do.

Yes, so as to simulate the car being on the ground, although the best way is to have it on a drive-on lift with its weight on the wheels. Sorry about the confusion - both left and right lower control arms at the same time.