Thanks. I'll check that. I failed to mention that the motor was replaced. I'm not certain if the problem started then or was like that before. It's a one owner truck but does have 200.000 miles.

 

there are no warning lights on

 

Doubtful it's the TRS. 1-3 work fine, then doubtful the TRS is off/bad.

What is likely here is that your OD band is not applying. Because you can make it go back in to 3rd with the OD switch, that tells me that your trans is getting the signal to go into OD, but something mechanical is keeping it from going. There is a snap ring that is a common fail point for the OD servo. You can find this easily by dropping the pan and having a look. I'll try and see if I can find a picture....

 

This is a 4R75W that my Buddy was working on.... these pics show the location, and also how the snap ring likes to sheer off.

 

Hell... even better. Found this on Raybestos' website. Explains a little better than I did. That servo is under a lot of pressure, BTW. My friend did not use the pressure relief tool on this because the ring was already broken. Doing it from under the truck, I have heard of people rigging up a floor jack CAREFULLY to both hold the servo in place for snap ring removal, and also for reassembly. I have no experience with this method, however. Badshoe sells a pretty sweet tool for the AOD/AODE/4R70/4R75's if you can find one.

https://www.raybestospowertrain.com/...d-not-applying

 

Awesome information. Thanks for the help.

 

I would suggest very little about automatics to anyone beyond get an a manual. My other suggestion, from the manual was "run the self test."