My transmission doesn't slip, and it's tough as hell- but when it warms up it won't shift. This is like after 5 miles. I'll put it in D and it will stay in first gear until I drop it to "2" or neutral while driving. Then it will shift, after a little work. Then if i let the pressure off from the engine it will shift back down. When I drop it to neutral I'm not really stressing it that much, as I got b!tched out for on other sites. I can pretty well match up the RPM with the speed, but the thing is when I put it in "2" or Second gear, it goes to first gear anyway. And won't go to second. A while back My tranny lost sense of all gears and i could move the shifter up and down on the column with it only randomly falling into gears, in no particular order. I found out that the linkage had fallen out of a lever on the chassis between the body and the transmission. That's what I assumed, because it fixed itself at one point. i have a TH350 in a 1978 K5. I've thought solenoid problems- anything else maybe?