What could cause my AODE (or 4R70W) to lose 3rd gear, and Overdrive?

This could be a small or large problem. We will start with a possible cause that would not require transmission removal. If the car shifts from first to second, and then stays in second, never shifting to third or OD it may have a number 2 shift solenoid that is failing to activate, or failing to seal when activated. This could be caused by a defective solenoid, wiring problem, or bad processor. If you have had any recent electrical problems one of the above problems is more likely. This same condition could also be caused by a stuck 1-2 shift solenoid in the valve body. If your transmission shifts from first to second, seems to hold second longer than normal, and then finally neutrals out completely at the point where it would normally shift to OD then the most likely cause is a damaged Direct Clutch Pack. This would require transmission removal and disassembly to repair. The Direct Clutch pack is the last one to come out of the transmission during disassmebly, so plan on a complete ... more