need trans guy help

96 1500 pickup 5.2 automatic...trans stared to act funny, on way home od light came on..... so i pulled codes that night.. po740 and po753. cleared codes and drove next morning 20 miles @ 60 mph. (live in the sticks). trans started to act up so i turned around to go home.... in 10 miles trans smoked ... changed trans and torq with salvage yard items . trany pulled good so i drove to work 40 miles @ 60mph...on way in on highway all of a sudden it felt like someone put it in second gear. ...select od off and baby it to work...fluid smells bad now... checked codes no faults found....any sugestions ...any known problems with this kind of trans?...thnx in advance..tim