O/D light flashes then 1&2 gear kind of jerk into gear all the other gears shift fine and when the o/d light is not flashing gears shift fine we just orderd a big transmission cooler what else do u think it can be please help

 

Could be bad shift solenoids

 

Torque converter locked up. Shifts hard and when it wont unlock it flashes the OD light. I have a lock up switch on my TC and thats exactly how it acts when it wants to unlock and the switch overrides it