92 4x4 vortec 6 jimmy, fluid level okay, not slipping, upshifts at low rpm no matter how much throttle you give it. won't downshift with part, mid, or full throttle. vacume line to tranny held vacume. how do i further check vacume modulator, kick down cable?
there is no vacuum line to the tranny only to t-case. your problem most likely lies in your throttle valve cable (often mistakenly called a kick down cable) the proper adjustment is to have the cable pulled as far as it can be when at full throttle. My bet is that yours is out of adjustment, unhooked, or broken
WARNING!!!! you can VERY quickly burn up your trans by driving it without a properly functioning tv cable
You nailed that one, the cable was out of adjustment. I was mistkenly thinking that was only for WOT. Somewhat coincident with this problem was the start of a leak, only at highway speeds, from inside bell housing. After reading this cable also controls line preasure, maybe the leak was from too high line preasure, and will be fixed too.
No idea how it got out of adjusment.