no 1st gear 2000 ram 1500 off road

46re 4x4 so my truck started limp mode code was
p1756 governor and pressure sensor replaced with
new fluid no change the truck starts off in 2nd gear
in drive and if I manually select 1st it sometimes
goes in sometimes it doesn't now I don't know
where else to look for repair and definitely don't
have the money for a rebuild it did have a newer
motor put in before I got the vehicle but it was
shifting fine up until this week then I did the repairs
and still no change what else do I need to look at