Hi guys, I just bought a 2001 Mustang GT with the 4-speed auto (152k miles), that was rebuilt at 141k miles, so should be relatively fresh (also had 3.73 gears installed). All that work was done with the second to last owner. Just recently had a overheating problem fixed (thermostat), and out of the blue I am no longer able to drive into 3rd/4th gear. The car just accelerates from 1st to 2nd normally, and that's it. A curious symptom is that when left in drive, and I'm pushing on the gas pedal, the car acts like it's revving in neutral, until you rev past 3500 (which is where you get acceleration again in 2nd). What could be the problem? Solenoid? Shifter not being recognized from being in Drive? I have no CELs at this time showing up (may not be showing up at all, as that same second to last owner straight-piped the car and had a custom O2 sensor to hide the missing catalytic converters). Appreciate the help I can get. I have attached the original workpaper from the transmission shop that did the work (number is disconnected, and text is very faded, I can't read it).