ScottTheEngineer

Hello,
I recently bought a 99 Jeep Grand Cherokee for 800 bucks. I planned to purchase only the engine but when I saw the body I found it was in better shape than the one I was going to fix.
The engine had a knock which, I found out after pulling the oil pan, was a broken piston skirt. I pulled the engine, had it bored .030 over and rebuilt it using a Titan Engine rebuild kit from Ebay. for 1500. (still cheaper than a used junkyard engine in an unknown condition.)
I got the engine installed and connected to the tranny, connected all the electrical parts threw in the battery and fluids cranked it up and it started almost immediately. No engine codes at all.
It had a pretty bad tick to it so I pulled the manifold cover again and checked my rocker arms sure enough I missed one (I installed the head while it was hanging from the hoist and it was 14 deg so I was in a rush.)
Retorqued all my bolts, replaced the head cover and started it up runs great and quiet.

I took it for a test drive and found that it won't shift into 4th gear (O.D.) The toggle switch comes on and off according to the display.
I checked the fuse and swapped the relay to for the ASD relay and no change.
I didn't get a chance to drive it before the rebuild as I didn't want to hurt the engine any more than necessary so I don't know if this is pre-existing.
I changed the transmission filters and pan gasket while the block was getting machined and the Fluid that came out looked old but not anything abnormal.
I've been checking the oil and tranny fluid after every test drive to verify there isn't any water from seal leaks or anything of the kind. The fluid levels are perfect. No engine codes at all.
Any suggestions on what to check? I'm about to go pull the front calipers and replace them as the driver side locked up on me on the last test drive and I found from experience that paying 100 bucks for a new set of calipers is always cheaper than a 200 dollar tow bill. Seems like I've replaced calipers on every car I own this year.