I have a quick cruise control question on a 1990

My cruise control works fine on my 1990 4.0 AW4 XJ. Except when I hit large hills the servo won't pull the throttle far enough to kick the tranny down into 3rd gear. And as you would guess it won't maintain speed on the larger hills because of this. I noticed the cruise control cable has quite a bit of slack in it, and was wondering if there was a way to adjust the cable inside the servo? I've already fixed the vaccum issues on it, so this isn't due to a lack of vaccum as there are no leaks anymore. And the TV cable is adjusted properly, as I can over ride the cruise control with my foot and it kicks down into 3rd gear and speeds up no problem.

I would suspect the TCU side of the TPS being at fault, but I still have not gotten my Cruise to work on either jeep.

Trans switch in power or comfort mode? Is the "trans" fuse blown in the fusebox?

The trans is in power mode and the fuse is good. The tranny functions as it is supposed too. It's the cruise that won't pull the throttle down far enough to get the trans to kick down. Thats why I was wondering if there is a way to shorten the cruise control cable to take up some slack in it.