if GC stands for grand caravan I have seen a lot of broken axel shafts which is an easy fix, I have also seen a number of them snap the splines out of the planets that means removing the trans and taking it completely apart.

70 duster full chassis super pro 416 CNC Indybrock heads 727 w/brake

best so far 1.212 60 6.219 in 1/8 at 110.88 9.768 at 137.81 1/4