My throttle valve seems to defy the adjustment procedures.

I push the slide all the way in, release the detent, and press the throttle to the floor to set it. In this setting, the transmission downshifts way to often -- like every time I accelerate or go up a hill.

I've made adjusements through the entire range of the adjuster and it seems there's no medium. It either downshifts too much or not at all.

What gives? Does this hint of a greater problem? I have plenty of fluid, BTW.

 

I push the slide all the way in, release the detent, and press the throttle to the floor to set it. In this setting, the transmission downshifts way to often -- like every time I accelerate or go up a hill.

It should downshift if you apply more throttle to accelerate or pull a hill. How easily it downshifts also depends on how fast you are going and the gear ratio you have in the rear. If you are running 1500-1600 rpm in OD, it won't take much throttle to downshift. Also, the 'downshift' you are feeling may just be the Torque converter unlocking. Try this, when you feel the downshift, grab the shifter and pull it down a gear. If it has already downshifted you won't notice a change.

 

It never occured to me that it might be the lock-up. I did as you recommended and there was no change so that tells me it is downshifting and not a lock-up problem.

I should better describe the prob. On a level surface, I can't even maintain speed w/o it downshifting and upshifting, back and forth, back and forth. It will even downshift when going downhill! It does this at half-throttle which I think is really wierd.

So today I moved the slide all the way out to put as much slack in the system as possible and I think there is some improvement but it still shifts back and forth way too much. Could there be another adjustment on the transmission side of the cable?

It's not slipping either because when I disconnect the cable, it no longer downshifts. Problem with that is it makes an uninspiring ride even more-so.

 

This sounds like a classic case of a bad VSS. If you don't have a scan tool disconnect the VSS connector on the tranmission and see if the problem goes away. Other stuff may not work correctly as you do this, but ignore it.

If you have a scan tool observe the vehicle speed during a steady cruise.

When the VSS goes bad (or starts to) the ECM sees an ever changing vehicle speed. In turn the ECM then locks/unlocks the TCC in accordance
to the ill-reported speed.

RBob.