First this is a great transmission. It is the same one that is in the Colorado pickups and it is tough! Mallet doesn't do anything to the trany when they put the 400HP Vet motor in one. Just the flywheel, clutch and pressure plate are changed.
Now for all of to figure out what might be wrong. Does it do it in any other gear? Also when it grinds is the shifter handle all the way forward? It could just be the linkage is off a little and you think it is trying to go in but it wont go any farther so it grinds. Grinding is usually caused by the gear not being fully meshed.
Big Phil is my Technician.
Hey Phil have any ideas?