You know, I'm a mechanical retard. It can take me days to fix something a mechanic takes hours. I can drop a bolt down into an engine an take 45 min to find it and get it out. But I love electronic stuff. I've learned how to reach wiring schematics just by coming up with fun stuff looking the shop manuals for other cars.
I've always thought about switching the + and - shifting, and also having the car go into sport mode when you come out of N down into D, and having it go into "normal" (non sport) mode when you shift over. One thing I HATE is driving the car in sport mode and then having to go into reverse and the shifter down into "upshift" when you think you're going through N to get to R because you forgot you were in sport mode.
I was worried there was a circuit in the shifter that sent some kind of pulse signal/language to the trasmission like the GLAM (whatever thats called) way the radio/HVAC/onstar/XM all talk to each other.
Anyhoo. Book 4 chapter 17 is transmission. Page 426 shows the mechanical arm going to the transmission only moves from D N R P. That means once you've moved the level to D, going from sport to normal and + and - are all electronic signals, the arm doesnt physically move when you move the shifter anymore.... thats good.
Page 288 shows the BCM gets two wires from the shifter level circuit. Thats not good. Only way to send that many signals through two wires is with a signal. Not a simple 4 wire setup. But the circuit diagram also shows 4 simple switches on top of the circuit. One switch each for "auto" "select" "+" "-". This makes me think there should be simple mechanical switches that open/close and tell the circuit which way the level is sitting. However, I cant find anything in the manual about how to take apart the shifter mechanism and fix/service anything. That makes me think its not a serviceable part and just gets replaced.
The "shifter control assembly removal procedure" (page 424) shows how to replace the whole unit. It shows how (after removing the shift rod linkage under the car) you unplug the circuit board at the bottom and remove 4 bolts. However, in the picture, it shows 4 wires coming down from the shifter to the circuit board. This isnt a circuit diagram, its just the picture to show you were the 4 bolts are to remove the whole thing so you can swap in a whole new unit.
So guessing from the picture, you MIGHT be able to take the unit apart, swap the wires for the physical switches, so that when the go the circuit board the circuit thinks your shifter is in a different place then where it really is (swapping + and -, or swapping "normal" with "sport").
If my G8 wasnt my daily driver and not under warranty, I might be inclined to remove mine and mess with it. But is is, so I'm not. If I had a junkyard shifter in my hands, I love to see if I could do it and then swap it into my car and see if it works. Do I want to swap my controls around enough to buy a junkyard shifter? Nah.
Here is some logic tho: You basically have 4 yes or no switches. DRIVE SPORT + and -. One will always be yes while the other 3 are no. From the factory you would be DRIVE yes and be in normal mode. SPORT yes and be in sport mode. SPORT yes, then quickly + yes or - yes as you shift up and down, then you'd be in sport manual mode. Swapping + and - should be logically ok, but if you swapped SPORT and DRIVE, then you'd be DRIVE when you move the level to the right, and after you manually shift to + and -, the car will think you're back in DRIVE and not SPORT. So you manual shift ability might not work if you switched SPORT and DRIVE. Or maybe it would?
Anyone have a junk shift assembly handy and feel like taking it apart?