T56 first gear grind

[vette427-sbc]

My dad has a T56 in his Tri-five and has been experiencing some issues with it... While in first gear coming to a stop (clutch still engaged) the trans makes a grinding sound as if you were trying to throw it in reverse. It only does it when the car is moving and in gear. It does it hot or cold. Doesnt happen every time, but it happens often. Any ideas on what it could be? Or any tests we could do to narrow down the possibilities?

[vette427-sbc]

Bump.....
Any ideas??? We're stumped over here