tranny question

I gotta jdm b16 with an lsd y21 tranny.. I just put in a new clutch and flywheel.. Car ran fine until a week after, When I back up with the clutch all the way out the car stops instead of drifting back..It only does it in reverse and I jacked the front end up and it doesn't do it maybe back brakes...I have no idea anyone have any solution to my problem thanx alot for your help...

I guess no one knows what I am talking about...