Welcome to the B Zone!
What trany do you have now?
Ford used a few different ones for the Bronco, the E4OD, AOD, C6 just to name a few.
E4OD = Electronic 4 speed with OverDrive (Has a button on the dash for the overdrive)
AOD = Automatic with OverDrive (the overdrive is on the shifter, usually will show D with a circle around it then D 3 2 1 or D 2 1)
C6 = Just an automatic with out overdrive.
My guess is you have the E4OD. That one did have some problems early on but over the years Ford made some improvements to it and now it is (IMO) the best one.
I would say stay with the E4OD (IF that is what you have) but get a newer one, 94, 95, 96 should be new enough to have most all the improvements.
If by chance you have a manual trany, I don't know much about them. I am sure someone can help you with that one.
Good Luck!