1993 chevy c3500 shifting issues

[Mdr8one]

So my c3500 1993 won't shift out of first. It has reverse and first gear. It has sat for over a year now. Fluid level is actually a little over, and I put in slip stop recently? Need some help.

 

[Will L.]

Iirc 93 is still tps? If so, make sure the tps is adjusted right.

Was the transmission slipping before, then you added the slip stop juice? And after that it won’t shoft out of first?

If not, and it just won’t shoft out so you added the juice- go the other way. Drain and replace all fluid and new filter. Adding a slip stop wont help something shift if the fluid is already to contaminated, thick, and has check ball sticking.
Absolutely NO dexron 6.

More details can help...

 

[WarWagon]

Pull codes! Trans ECM doesn't pop the SES light for codes as it isn't "Emissions". Yes the 1993 is a TPS on the DB2 IP.

 

[THEFERMANATOR]

Without codes you're doing nothing but throwing money at it. Diagnose it, don't burn money.