Hyundai Repair: 1997 Hyundai Accent GL, hyundai accent, forward gears

Question
We have replaced the automatic transmission in my 1997 Hyundai Accent-however, the transmission will not go in drive-the reverse works fine but that's it.  The old transmission was burned up but the replacement is not. The car starts right up and prior to the transmission problem, it ran great. The car has a little over 100,000 miles on it. What more can my mechanic do? (Older American models are his specialty.)  

Answer
if you are useing an older trans to replace the old with he might want to try an run a presure test to see what he as so he knows if it has any at all in forward gears also does it go into any other gears like low these thing would need to be knowen so i can say more so sorry hope this helps