Why won't my truck shift into overdrive? on 1994 Dodge Dakota

my truck will not shift into overdrive and the speed odometor does not work either. i replaced the speed control sensor and checked the gear for it and still it is not working. i was told that there is a speed buffer or such but i have not idea where to find this on my truck

1 answer
Were you able to get this resolved? Did you get the diagnostic trouble codes in the transmission checked?