i have a 96 blazer 4x4 with the 4l60e. ive researched the forums and found all the known issues with this trans, but mine is somewhat different than others. i have no 3rd gear, it shifts from 1st to 2nd, but trys to go to third and just revs up. i changed both solenoids for the heck of it, no change. no check engine light, no codes. (ive heard that if you unplug the trans plug harness the trans goes to 3rd gear only) so i unplug the trans connector and 3rd gear works and pulls fine, so the clutches should be good correct ? So im guessing it has to be a electrical type issue instead of mechanical. any clues to where i should start ? any help would be appreciated.

ive heard a possible ground problem from the computer, where would i look ? are the computer grounds location ?

 

A stuck 'on' shift solenoid B could possibly cause that issue. Since all of the solenoids receive constant +12V power and the grounds are switch by the PCM to activate/deactivate them, the wiring for the ground could be grounding out somewhere either inside the transmission or between the transmission harness connector on the passenger side & the PCM itself. You can find the wiring schematic for shift solenoid 'B' in the applicable OBD2 code post (see signature links).

Please have patience and edit your post if no one has responded and you wish to add further information/questions.

 

can you tell me where it grounds to ? is it on the frame or motor ? i was checked the wirings around the computer and noticed that my factory computer was one of those that needed the gm vcm jumper wire fix, so i found out from here what wires goes to where and instead of paying $50 for a wire from the dealer , i made my own and went for a test drive and 1st and 2nd shift better than before, but still revs once it hits 3rd. does anyone have the pinout diagram of the round harness that plugs into the trans ? thanks