Question

Does code P0750 have anything to do with my 1999 Ford F150 4.6L not shifting gears? Transmission only shifts from 1st to second then no more shifting

Answer 1

P0750 SSA solenoid circuit failure

Yes this does, the shift solenoid  comes in a assembly, the fix is replace the shift solenoids

Answer 2

P0750 Ford Code - Shift Solenoid 1 Circuit Malfunction
Read more: https://www.autocodes.com/p0750_ford.html

P0755 Ford Code - Shift Solenoid 2 Circuit Malfunction
Read more: https://www.autocodes.com/p0755_ford.html