Adam Rouillier

Hey everyone, I am hoping you all can help me solve this issue. I have a 1996 Ford F-150 with the 4.9L EFI Inline 6 and Electronic 4-speed Auto Transmission. My transmission runs great for a little while then the Overdrive "Off" light starts to flash. The truck still drives fine but the shifts are very hard. When this happens, I can no longer turn off or on the overdrive. Also the shift form 1st to 2nd is the hardest with each shift getting better down the line. Driving style appears to have no effect on this either. Another curious face is that I can stop, turn the truck off and back on immediately and the issue will be clear for a few minutes. Recently had the transmission completely flushed and added new oil with no luck. The only code that is showing in relationship to the transmission is Torque Converter Slip which, frankly, does not make any since what so ever. Some times it will do this every time, every day that I drive and other times, I can go months without a problem. The mechanic has not been able to figure it out either.

Has anyone experienced this or know what is going on?

Marc D

Torque converters work with centrifugal force of the fluid, locking the coupling inside. When they start to slip it takes more RPM to lock it up and engage the transmission. First to second is the heaviest load so it will shift the hardest because it grabs all at once. It's also possible one of the electronic shift solenoids is sticking but only a trans shop can tell you which one by testing them. Good luck.