Hi i just installed a new ford 415 v 10 in my 1999 fleetwood bounder motor home before putting motor in transmission work fine. Now i only have reverse gear . Does anybody have a clue what it could be it has new flied in it

 

I would think you removed the engine and trans at the same time, with that in mind,
check all the electrical plugs that were disconnected. Sometimes p[ins get pushed out and don' make contact.