94 Suburban 1500. Has no reverse or any other gear with the TCC plugged in. Unplugged the TCC and I can manually shift through the 4 gears and do 90 plus mph. So it's an electronic issue. Any guess??? Help!!
The TCC is the Torque Converter Clutch, which is controlled by a solenoid operated valve. If the solenoid fails and gets stuck open it leads to the symptoms you describe, called torque converter lockup. Replace the TCC solenoid and your problems are likely solved.