Overdrive Turns on real quick then off around 35 mph

[1998RamMan]

Looking for help on a issue(?) with my 1998 Dodge Ram 1500 46re. When Im driving at about 35-37 mph the truck jumps into overdrive for almost excatly a 1 second. It jumps about 400 rpm or so. After that "hickup" it drives fine in overdrive afterwords when you reach 50 mph+. On the graph, you can see where it kicks in at the spike at about 35 mph. When I take O/D off, at that exact point the truck shifts and lowers rpm.

Ive checked all the fluids, fine. No visual leaks, no codes. Ive noticed the truck starting to do this in the past few days. Yesterday I tightened up my TV cable and took some slack out.

Any tips, suggestions?

 

[1998RamMan]

***********UPDATE***********
I brought it into the transmission shop a few months ago and they were able to rebuild it. Turned out it was the 4th clutch piston that got worn out, hence why is was being funky going into overdrive.​

 

[huntergreen]

Thanks for the follow up.