47RH Trans upgrade
 

I have a 95 Dodge Ram 2500 4wd with 47RH it will not go into overdrive was told by my mechanic that the overdrive seal is bad. So I need a little help on which way I should go. Do I rebuild the Trans that's in it or buy a new one that's built? If I go with a new one what's the best one to put behind a cummins? Planning