Initially I had the OD and lockup controlled by adjustable pressure switches, but I didn't have any vacuum switches for kickdown / unlock. I had it set to upshift into OD at 48 mph and it would automatically downshift back into 3rd at about 45 mph. Lockup was set at 55 mph which would automatically unlock at 52 mph. Those upshift speeds made sense for my setup at moderate acceleration, and the downshifts were just how the pressure switches function.
Without the vacuum switches it didn't matter how much or how little throttle I was feeding the car, it would shift at those points. And no automatic kickdown whatsoever. I had rocker switches so I could manually disable / shut off both OD and LU, so it was manageable.
Here's what I didnt like that i had no way to manage: it would downshift into 3rd too soon. OD is a freewheel gear, but 3rd is not. So when decelerating from 50 mph (for example) I would really feel the downshift from OD to 3rd as the rpms went up to about 1500. And when decelerating from 70 mph (for example) the LU would hold until I hit 52 mph. LU is not a freewheeling action, so until it unlocked there would be a similar dragging feeling. Still a million times better than 3 gears and no lockup, but not ideal.
With the factory PCM it works like you already understand from your more modern vehicle. At light throttle it goes into OD then LU as soon as it can. More throttle = later upshift, and of course kickdown when required. When in lockup at cruising speed it will unlock as soon as I let off the throttle and allow the car to freewheel and gently decelerate. I think you might be able to get it pretty close to this if you spend the time to dial in your vacuum switches and pressure switches.
