Dresser td7h

:Banghead cannot seem to figure this one out .My dozer started acting up after a steep climb on a creek bank.I first lost all forward movement,but later regained that.I brought it home investigated the suction screen and filter ,both had clear thin plastic pieces in them .Mech. told me he had never seen this before ,but looked like posssible the glue aroung the bottom of the suction screen. heres whats going on ,sometimes it stalls the transmission under a load and the next time it might act just fine .This happens both foward and reverse.what is the the possibility that some of this has gotten in a control valve.