Can turn on and set. Won't hold speed. Runner drops 1500 rpm then downshifts. Doesn't matter what speed I set it. What are obvious connections to check?

My cruise is also notoriously crappy.

I think it has to do with the gutless engine and oatmeal in a bucket that they pass off as an automatic transmission.

I always set the cruise about 5 mph higher than needed because it always drops some speed initially. I don't even bother with the accel button because it will actually slow the thing down unless I push it and hold it for about 5 seconds, at which point it will down shift and lunch the thing forward.

It will not maintain speed even on a slight incline. Once it drops by about 10mph the thing kicks down and the engine revs almost to redline causing it to over shoot the set-point by about 10 mph.

The only thing that seems to work for me is to hit the O/D off button (on the shifter) before a hill to make it down shift early and the extra RPM tends to help it maintain it's set speed.

I sorta agree. But it's more the engine than the trans.
Neither one (4 or 6 cyl) is ideal behind an auto trans.
That Toyota trans has been around for decades in one form or another and is solid.

Yes , that's how it works...when it works. Mine isn't working. Runner will cost to a stop, if allowed. Need to know what to check.

Check to see if your e-brake is all the way in. Sometimes I have to push the lever in to make it work.