[Morley]

No kickdown cable in any 3rd or 4th gen they had/have throttle valve cables, different animal.
In 94 the 4L60E transmission was introduced in the F body line. This is an electronic transmission, no TV cable either.
You could have a stuck servo valve (no idea how to unstick it on a 4L60E), a blocked passage in the transmission, low fluid, dirty fluid & filter or a transmission on its way out.
Check the fluid. If it is brown or burned smelling, you got problems.
Why did you rebuild the trans? If it was because it "came apart", then you may have screwed yourself by not replacing the converter. I know torque converters are expensive but they should be replaced when you reduild/replace a transmission, especially if the transmission broke down. The converter can/will hold dirt, transmission fragments & other trash in it. Also if the trans shelled out it could have been caused by the converter or the converter could have been damaged by it and is waiting to let go itself.