Paul Scerini

So I have 2005 2500hd with a 8.1 l. With a Alison Tran. Won’t go in reverse changed n s b u on outside of Tran on driver side and cleaned plug and ingtion switch as well. But still no reverse and also still says on dash range shift inhibited Change fluids no chunks of metal both filters Bought as is with no reverse was use buy city they have a p t o. Unit on motor as well ? Any help out there on my reverse don’t know how well drive is but does move in drive. Thanks folks Pauly