I drained the transmission to replace the o ring on the manual shift linkage. To remove the manual shift linkage you need to disconnect it from the detent lever. I replaced the o ring on the shift linkage, reconnected the detent lever, replaced the filter and pan gasket. Filled the transmission with fluid and started the car. No gears...no drive, no reverse. The park position will not hold the car....It tries to hold but will "click" through the park position.
Does anyone have any suggestions on what I might have done wrong?

Is this something I can fix without dropping the pan again?

thanks

 

Welcome.

There are only two options here. You either didn't properly attach the external linkage or you didn't properly reinstall the internal linkage. The outside parts are easy to inspect and work on. The internal parts obviously require the pan to come off. This is a very simply linkage. There aren't a lot of failure modes here.