GordnadoCRD wrote:
At the same time, I'm hoping I can get the TCM to engage 4th gear at 40mph instead of 45, and 5th gear at 50mph rather than 65.
Having manual control of the TCC engagement would allow me to maintain lock even to speeds down to, say, 35mph, and if enough torque is called for that it would shudder, in situations, such as passing, I can manually release the clutch to programmed mode until normal throttle conditions are established again.
I'm thinking having the selector switch on the dash side of the steering wheel, and using the unused portion of the clockspring to transfer the signal down the column. Either that, or a less convenient switch on the passenger side of the transmission gear shift knob.
The vast majority of my driving around here is 50mph or below, and not a lot of stop and go, so manual control makes more sense than having it lock / unlock at 57 mph as it does now.
I too have though of installing a switch to control TCC application.
But there are a couple issues with that.
1. If the TCM sends the command to apply the TCC and doesn't sense the change at the input speed sensor, a code will be set. Will that force some sort of limp mode? I don't know.
2. The TCM uses PWM to the TCC solenoid in order to reduce the shock of applying the TCC. Manually turning on the TCC without the proper PWM duration will cause a harsh apply of the TCC and might make the shudder problem worse or hurt the clutch in the TC.
If you want the upper gears and TCC to apply at lower vehicle speeds, try a used Hemi TCM. They are pretty cheap on ebay.
Mine will apply 4th gear + TCC at about 41mph under light throttle.
And 5th gear + TCC can apply at about 47mph under light throttle.
With OD-off, 3rd + TCC applies at 30-35mph.
You can also look for standalone transmission contollers for the 545rfe. They exist, but are a lot more $$$ than a GDE trans tune and will require significant time dedicated to tuning and getting the shift points exactly right.