Did over drive (5th) work before you put the new bearing in the transmission?
If it did, I think what you might have done is assemble the 5th gear parts incorrectly. In that case, it would be pretty simple to pull the tail housing and check that stuff over.
Otherwise, you lost over drive... 5th gear will be the first one to go if the transmission fluid runs too low for too long.
But... check everything over first, maybe you forgot to assemble something simple this way instead of that way.
My guess is the shift fork for 5th is not in the proper place.
1996 Ranger 3.0, 5 speed stick, 4x4, 3.73's, 31" BFG AT KO's
Wiring, it's all fun and games until you poke yer eye out with a soldering iron...