Hey guys, been gone for awhile but finally got another Cummins. It's a 97 12 valve crew cab conversion. The conversion company didn't wire in the rear doors the best so I decided to wire in new switches and clean up the wiring. I get done with that and now my transmission is stuck in 3rd. I can manually get it in 2nd. Also, when shifting into reverse or drive it seems to slam into gear now. If I'm rolling back very slowly and put it in drive it slams into gead

 

Also, pulled codes and got P0743, P0753, and P1765