318 MAX fuel economy builds?

autopar3000 said
You can't use the factory pcm to *only* control the transmission because it wants too much data. Well, I suppose it's possible, but by the time you put in the effort to set up a vehicle speed sensor, throttle position sensor, crank sensor, and maybe a MAP sensor you might as well go full EFI.

And if you want a full EFI engine and computer controlled OD transmission in a vintage Mopar then the Magnum swap so obviously the way to go. It's a drop-in setup anyone with some knowledge of automotive wiring, the factory service manual, and access to Google can do themselves.

There are a some standalone controllers out there that will manage the 4Xre and 4Xrh transmissions on a carbureted engine. I just found this, but I know there's at least one more I can't find right now:
E-Trans Control

If you're building an LA engine (or any engine) for big power EFI you can use the Holley Terminator, which will also control the OD trans:
Holley EFI 558-473 Holley EFI Transmission Control Harness - Chrysler 46RE

But the standalone controllers aren't cost effective if you already have an RH transmission like your A500. Just use the pressure switches and vacuum switches like you're planning to do. They work fine, albeit not perfectly. I'll explain "not perfectly" in a separate post.

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.