1985 745 w/ D24T, M46.

Shudders on takeoff, worse in reverse. New motor mounts, trans mount.

Replaced cracked front crossmember with newer reinforced version. U-joints and center carrier check OK.

Shimmed/raised the center carrier approx. 1/4", helped some.

All the above did help some but shudder persists.

Yesterday found some level ground and with car off and trans. in 1st, rocked the car back and forth by rolling a rear tire while looking at the driveline. There was noticeable up and down movement at the differential pinion nose.

Earlier I had tested the rear suspension bushings when the car was up on jackstands. Prying w/ a prybar did not show any bad bushings but maybe I did not know exactly what to look out for?

Before I condemn the clutch itself, is that movement at the differential front normal? Where do I concentrate on to solve?

 

If it's while you are not fully clamped on the clutch (where it's still slipping) I would think that some clutch parts are warped. The bushings would just make it work. The center drive shaft bearing rubber mount was my first thought. But that shows up at lower RPMs, with a heavier load and under higher throttle. All bushings should have a bit of flex to them, but if they are missing chunks and allow the mount in the center to be at rest out of center, then they are shot. It really sounds like you checked all that, so you may need to have the flywheel resurfaced and put in a new clutch. The other option is get a GoPro and do a bunch of starts while having it look at the bushings. See what's moving.

 

Your Pressure Plate is likely glazed. You can use new clutch...