Does the shudder ONLY occur when the clutch is being slipped?
I was thinking some issue of a shot driveshaft/half shaft that works the centre diff that’s shot. But that doesn’t work out as the centre diff would be under most load when going hard in this situation. Plus you’ll hear the typical knocking when doing a U turn in either direction. So that’s out.
Other thought if it’s occurring when slipping is that the pressure plate is warped or the flywheel is full of heat stress cracks/wasn’t shaved properly.
Last out there thought is your flywheel is loose, but this usually results quickly in other issues, like the flywheel parting company with everything else and exiting out the bell housing in whatever direction it feels like...
Ok, last last one! Got any codes? Maybe you have a partial misfire or some issue where a cylinder is down on power at low throttle but makes up for it at full throttle for some reason. Or you have fuel pressure issues...
Cheers
Bennie