how can you tell if tran is sliping i am looking at a blazer and usualy do a stall test but this blazer does not have a tac it is a 96 131000 miles

also will it send a trans code if sliping is sensed

Easiest way I know of is to drive it normally and listen for the engine speeding up when it shifts. If you hear a brief increase in engine speed when it's shifting that is usually an indicator of a slipping transmission.