96 Rodeo Auto No Reverse

I bought this 96 Rodeo LS, Auto 4X4 about 1 year ago for $500.
Got it for the Price because of No reverse, I have done nothing to find/solve the problem.

All drive/park gear/s work good. All Indicator lights work, 4x4 works.

When I place shifter in "Reverse" I can feel it Engage, and if I'm on a Super Flat spot, it will roll about 3" in reverse, and I "Think" in Neutral.

Lady I bought it from had Motor Replaced about 10k miles ago, and said F it after it stopped going in Reverse. 140k'ish

I Know Motors, I dont know Trannys, "thought" it might be Tork Converter?
Does it sound like a Sensor (from what I seen about other trans issues) or the Tranny shot?
Ty

well reverse is the first gear to go out if there is insufficiant fluid, best bet is to fill it up to specs and if that dosent help drop the pan and check for metal shavings. if theres more than a tablespoon then the tranny pan then prob needs to be rebuild

Check the date. I'd be willing to bet they aren't still waiting for an answer.