My high mileage Silverado had an episode shifting to O/D. It made the shift, immediately shifted into 3rd gear, then it tried 4th again, then settled for 3rd.. This all happened with fairly light throttle acceleration . About 40mph.
Using the information on this forum (Thanks to all who shares info) I checked the play at the 2/4 servo best I could. I tightened the clearance by adding "length" to the servo pin with my tig welder. The truck now has 4th gear ,but the shift is very loooong ! The third gear shift is pretty decent. The 2nd gear shift is sometimes soft and elongated, but sometimes it has a real snap or jerk to it. Both 2nd gear conditions happen with light accelerator pressure.
I realize it should be rebuilt, but now is not the time for me to do it.
Could there be an issue with the separator plate being worn. Any ideas to help me nurse this trans a little while longer ?

 

Issues with shifting for 2nd and 4th gear can be a sign of Reaction "Sun" Shell to Sun-Gear wear/ damage...
Especially if issues with Reverse also soon start.

Good luck!