OD not working with 12 o clock wires plugged into alternator, problem started after replacing the old one.
The complaint is pretty sketchy but the alternator should have nothing to do with the OD on the transmission.
This is ancient history but I think the OD operation on this unit is controlled by a TV cable which runs from the throttle linkage. The adjustment needs to be correct because not only does it affect shift operation but can also ruin a transmission is out of whack.
You might do a search on the net or Youtube for the how to on this.
The OP’s truck could have the E4OD. If it has the 351W or 460 it almost certainly does. The E4OD is electronically controlled and the first iterations of the transmission weren’t known for their reliability.
It does have the 460. How do I check to see what type of transmission I have?
If it has a button at the end of the shifter that toggles the OD off/on then you have the E4OD. To my knowledge it would be the only other automatic transmission option offered around that time. The C6 didn’t have OD. The E4OD did.
It does have an od off button on the dash, it started right after my alternator failed, if I remove the plug at the 12 o’clock position it comes back , but it acts like there is a miss fire or poor fuel flow