My 1993 GMC Sierra K2500 5.7 wont shift into any gear . ran fine I stepped on the gas to overtake a car to change lanes and as it started to kick down I decided to just drop behind the car and when I put my foot back on the gas it just revved like I was in neutral. no gears 1st 2and 3rd od or reverse

SOURCE: 95 GMC Jimmy 4L60E no 2nd or OD 4L60E

You might want to try this if its got a kick down cable unhook it from throutle body and pull it out as far as you can and let it snap back, do this a few of times, sometimes a valve gets hung up inside valve body of trans. and won't let it shift. If that don't help you may have to pull pan to dislodge it if thats the problem. chk. the plug on trans. (Its a 4 wire white plug) with test light with key on to see if there is power down there one will be hot, thats for overdrive, now on top of intake in front throutle body there is a sending unit that looks like a temp. sending unit with a 2 wire plug on it that sends a signial down to that plug when engine gets to temp. to let it shift to overdrive. Maybe this will help, or give you some ideas.

SOURCE: Stuck in 3rd gear

been awhile since posting..., try Solenoid A...better yet, the Trans fuse...

SOURCE: 95 GMC Sierra 4L60E will not shift down to 1st or up to 4th.

no power stuck in 3rd gear electric shop unless youve burnt it up good luck...www.TransmissionGarage.com

SOURCE: 4l60e no forward or reverse gears operating

It sounds like your torque converter or the pump is broken.

SOURCE: 1992 GMC Suburban not shifting into OD, Transmission Modulator?

The shift down linkage on the carburetor below the gas pedal cable might need to be adjusted to increase the hydraulic pressure on the internal clutch plates in the transmission it shows you how to do that in a car manual.