Mine does the same thing, Have not found a fix.
SOURCE: 2002 GMC Envoy is having
I ran into this concern with my 2002 and my wife ran into the almost identical problem with her 2003. this may sound silly,, but it was the clutch fan. Extreme loss of power from time to time came first. Then a roar of the what seemed like the engine when stopping. Actually cut off after it started to roar at highway speeds, and had absolutely no excelleration from time to time. Sometimes all of the symptoms completely went away. After taking mine to the dealer several times, finally they got it right and replaced the fan clutch. When my wifes 2003 SLt started doing the exact same thing as my 2002 had done, we both knew what the problem was, and the dealer did a quick fix. $600.00. Perhaps this should have been a recall feature, but never was. Everyone that I know that has an envoy, somewhere around the 72,000 and 103,000 mile mark has had this problem and have had to have the clutch fan replaced. It may sound like the vehicle is going to have to be junked,, but that is all it needs.
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: no reverse after rebuild on 4L60E Transmission from 1995 GMC Sono
There isn't a modulator on this trans as it is electronic
You can have first gear going forwrd but no reverse. It is possible. The low/ reverse clutch isn't needed to go forward.
SOURCE: i have a 97 gmc jimmy 4x4. the transmission goes
I need the CODES this year has valve body problems for tcc slipping on these & shift timing need more information
SOURCE: 95 GMC K2500 4x4, 4L80E transmission problem
VSS is still good if you have your cruise control and speedometer working, it's common for the wire harness to the solenoid on the passenger side to get corroded and or the sires to break due to the heat given off from the catalytic converter beside the transmission. Check the condition of the wire harness and clean the contacts with brake cleaner and reinstall with some grease to keep the corrosion away, hint use marine grease. Marine grease cost a few cents more but resist water longer and better then normal lutetium grease, I use it on everything and get longer life out of my u-joints and front end suspension. Most transmission shop will test drive free of charge and scan the truck for DTC codes that sometimes will not show up in the check engine light, but mostly you do have an electrical problem so check all your fuses and wire harness from the ECM to the transmission. Good luck and keep me posted, be glad to help you get your truck running 100% again soon without some transmission shop getting you to replace the whole transmission for $2,300. If you are going to have the transmission service, "fluid and filter changed" Have them replace your boost valve. The boost valve is around $45.00, the boost valve controls the amount of transmission fluid pressure and low transmission fluid pressure will cause the transmission to fail. I replace mine every second transmission service and i have over 365,000 miles on mine. Keep up the good work friend.
Testimonial: "Excellent information from the beginning.Thank you.I worked each of the connections I could locate and disc. the bat to clear the code. Good so far. "
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