[t vago]

So, for a test of this idea, I changed the tire size setting on the Durango. First, I set the tire size to a 32 inch diameter. Then, I pulled the transmission computer ignition power fuse, and verified that the programmer could not read the transmission computer. Then, I reset the tire size back to normal. Finally, I reinstalled the transmission computer ignition power fuse.

I took the Durango out for a quick test drive, and verified that the new lockup and 5th gear set points changed at 40 and at 45 MPH. So, the idea works...

Kind of. You don't need to worry about lugging the engine at low speeds. Once the Durango encountered any sort of hill, it disengaged the torque converter lockup and shifted out of 5th, if it had gone into 5th gear.

Lucky for me, the transmission computer has a wire signal input for the throttle position sensor. I might be able to come up with something that will fool the transmission computer into thinking the throttle is less open than it really is.