I have purchased a 98 dodge 2500 4x4 gas 360 engine , it has a miss and the transmission will not shift into o/d . I have had a nech. Do a complete tune-up replaced a injector and the intake gasket . The problem is still there , any help ?

. Check for codes.
. Drop and clean pan, change transmission filter, replace fluid. This is about all most people can do without facing a rebuild. Most ATXs are designed to go around 125,000 to 150,000 miles.

What did the tune-up involve?