My recently rebuilt 46RE transmission sometimes freewheels when running on the highway at about 70 MPH plus. It's typically in overdrive when this happens. When it occurred today, I slowed down a bit and the transmission finally seemed to couple back up with the motor and things went back to normal. I've also noticed that the shifts aren't as firm as they used to be. I don't drive this truck often and only drive it when I have a need for a truck or towing. The transmission likely has less than 5,000 - 7,000 on it since it's been rebuilt.

Transmission seems to be full of fluid.

Any ideas as to what may be causing this issue?

 

Were the electronics changed when it was rebuilt? Fluid still look good?

 

Yes, the electronics were changed as part of the rebuild and the fluid still looks great. The rebuilder did have to go into the transmission to change the electronics to the earlier year setup after the transmission was installed, as the PCM was thinking the transmission was overheating after 5 minutes of driving and kicking off the overdrive function. The change of the electronics solved that issue some time ago. The transmission also sports a deep TCI aluminum pan, too.

 

Think I would plug in a scanner, and see what governor pressure was doing when the problem presents itself.

 

Thanks for the tip. I will keep the scanner plugged in and ready the next time it happens.