Hello,
I am looking to buy a truck from a guy, but as it sits, it has transmission issues. He has all the receipts from a complete trans rebuild 50,000 miles ago, but he told me that it won't shift into 3rd or overdrive. I'm guessing it's the 46RE transmission. Anyway he mentioned that he was asking around and the consensus seems to be that it's an electrical issue. I'm not too familiar with transmissions but I was wondering if it could be a valve body/ solenoid issue. Also, could I do a diagnostics test to narrow it down?
Any info would really help!

Thanks!!