Hey everyone new to this site. But anyways I need some info immediately . I replaced my transmission tonight and took it for a drive and it has no power in drive and feels like it won't shift at all. Only stays in one gear. I have lots of codes it's throwing after that. PO740 PO748 PO758 PO865 P2761 PO713 and also while driving it. It would loose power and drop the rpms for a quick second then back up. But the rpms are at 2.3k rpms going 90kph. But have reverse and it works strong.

 

Is this a used or rebuilt trans that you installed? From your description and all of the codes you have, it sounds like the trans is in fail safe mode. In fail safe mode the only forward gear you will have is 3rd. Is the big electrical connect on the right side of the trans plugged in and in good condition?

 

Yup, sounds like the harness is not plugged in.