transfer case, speed sensor

Leak on speed sensor on the transfer case, New tranny two years ago, new transfer case last year along with 4x4.
Driving in highway, tranny won't go into overdrive, (automatic) won't
shift gear from 3rd to 4th or 5th. High rpm goes on up to 5 (90 to 95 mph) but wow power is there its nice but I don't want burn out my tranny. Parking it on my driveway and wanting to fix it this weekend.
I remember there is a truck tranny fluid that can stop or slow down the leakage and I forgot what's it called? Will those help me? My fluid level is above minimum level. Thinking about selling it after I fix the leak. Seems like 96 ram is worse year of dodge history.
Good day dawgs

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.