I have a 94' chevy 6.5 with a 4l80 had lost reverse which as little as I drive it was able to deal with but it started have a problem shifting past 3rd in the evenings but every morning shifted fine. Then this evening after making my loop so I could leave in the morning. I was sitting and idling while rolling up the windows heard a slight piping noise and so I put in reverse heard the tranny kick in and now I have reverse but no forward. Nothing in OD, D, 2,1 with or without 4 wheel drive locked in. Not sure where to look. With no reverse figures transmission was shot but with it going from one to the other thinking maybe something else.
Thanks for any insight.

 

If you unplug the main transmission plug on the side it will default to reverse and 2nd. If when you unplug it and still have no forward gears it's mechanical.

 

Ok thanks will test tomorrow.