I have a 96 ram 318 2wd single cab with 150,000 miles. The truck was bought used 3 years ago, and I am not sure if tranny has been serviced. It started the overdrive off yesterday.
I put 1/2 quart of ATF-4 as it appeared slightly low. Tranny fluid is clear and does not smell burned. We took it for a drive and all was fine for about 10 minutes, then the overdrive off came on. Limped it to AutoZone where it showed no codes. Limped it home stopping every 200 feet to turn key off and starting engine again so truck would move. All gears are disengaged before restarting.

I finally had my mechanic come over with his Snap-on scanner. No Codes-Engine ok and transmission ok. Vehicle would not move (cold). Putting it in reverse i could feel a reverse pressure, and a constant metallic sound from the torque converter area. Putting it in drive I could feel the same type pressure forward. No torque converter sound in drive though. But no movement.
Mechanic said his scanner would tell if no communication to transmission. Maybe the torque converter failed?
Need advice!
Sincerely, Ragdog

Disconnect the 8 pin connector on the drivers side of the trans. It's about halfway back, goes straight down into the top of the valve body area of the trans. See if the truck behaves any better. Keep in mind, you won't have ANY automatic function. So, going forward, you will have to start in first, and shift as appropriate. No O/D, or TCC either. If the trans works fine shifting manually, then you just have an electronics problem, and replacing them should fix it.

Does the trans temp light come on as well??

Negative, it does not. Now it does not move. I haven't left it running long enough for a temp light since I had to park it, but before that it was only the overdrive off light. No temp light during failure.
I will try your suggestion as soon as I can jack it up.
Any tricks to disconnecting the 8 pin connector?
Thank you for the quick response!
Sincerely, JJ

Also, we heard a rough sound for awhile around the torque converter area when running in park. The sound eventually went away. My mechanic said it was most likely the catalytic converter. Now I wonder though. Have not heard that in awhile, and the catalytic converter has not been changed. It sounded like loose bolts slightly hitting something.
My wife (the daily driver) says that it would rev way up if she floored the pedal. When she let off it would catch and be fine. Evidently it has been doing this for a while. She just mentioned this.
Hope this helps.
Sincerely, JJ

The connector can be fun, simply due to it's location. It's going down into a horizontal surface, so, dirt, and various other things like to accumulate there...... Clean it up a bit before pulling the connector.

Sorry for late response Life went on. Also the check valve was removed.
The tranny was rebuilt & all parts were replaced including electronics and torque converter. Now they even replaced the computer. The transmission shop cannot figure it out.
Now it runs okay for a few miles, the acts like torque converter is acting up and gives the overdrive off light. Have to restart & limp home.
Any suggestions?
Desperate

Sounds like it has the wrong temp sensor in the trans. That will cause all sorts of interesting issues.

TV cable maybe?

Your mechanic should have looked at what the pcm is seeing as for temp. Assuming it can read live data.