transmission trouble

I have a 99 Chevy Express Van (full size). 5.7 engine with 4L60E trans. I replaced the trans with a remanufactured trans and took for a test drive. The trans shifts way too quick and actually bogs down the engine when it tries to go into OD. I noticed that the Speedometer is reading way too high, something like 60 when I am actually doing 30. Any ideas what might be wrong? The rebuilt came from Autozone, has been dyno tested and the reason I replaced it was the old one quit completely and had metal in the pan. I have cleared the DTC codes and recently got a new code P1810. I am not sure the code is all that helpful as it tells me what I already know. Any ideas would be appreciated.

Update: not getting any codes now, but still shifts way too soon. Sounds like shifting a manual trans into high gear long before you should. Engine lugs.