HELP! Overdrive kicking out

andy

1998 Dakota with a 5.2 and a 44RE transmission.  I've had it a week.  The check engine light was on and showed a speed sensor fault. I replaced both speed sensors and it eliminated the check engine light. I also had the transmission flushed.Early in the drive, it shifts fine and goes in to overdrive, but once it is driven a few miles, it will automatically drop out of overdrive and it will not go back in until you turn it off and let it sit for a few hours. When the overdrive is working, you can turn the overdrive off and on with the switch in the shifter handle. When the overdrive is not working, turning the switch on and off makes no difference. Any suggestions are appreciated.

.it could be a bunch of things start off checking the fluid is it clean and not low...you could have a bad shift silenoid mine went out before my trans blew and i couldnt hit 4th gear being in 3rd doing 70 and doing 4000rpm was great gas mileage lmao