sounds **** bud
Try swapping the orig shifter back in to see if its related to the shortness
then do a oil change om the box-
If this dont help, see if the bushing that holds the shifter arm in place is still located correct.
if that isnt the prob.. then iŽd get a look at the prop, mabey the ballance weight is getting in the way , if the grabox bushes are worn badly