bendix shearing teeth

I have a 1990 ranger with a 2.9 liter v6. Is the 5 speed tranny include 4 speeds and an over drive or did ford do anything like that? The transmission is supposed to be a 5 speed for later models beyond when ford quit making the 2.9 in 1992. The question is, if the tranny is for the later model...

I have a 1990 ford ranger with a 2.9 and someone put a 5 speed( speed with od) and i was told the tranny was from a 93 model ranger. I need to know why starters keep shearing the bendix teeth off. Is there so much difference between the 2.9 and later engine flywheel diameters that the teeth go...