98 to 01 transmission swap
 

I have an 01 blazer 4x4 with 4.3 vortec. Transmission has no reverse. was given a 98 transmission but have been told that it will not work in a 01. can anyone tell me what the difference is. They both look the same & all the electrical plugs are identical. Bolt pattern are the same also. I don`t see why they cant be swapped out. but I need to be sure before i waste any more time doing this job. DON`T WANT TO DO THIS TWICE. Any advice will be helpful & appreciated. Thank You Bob.