Transmissions: The automatic/manual combination worked even better than we hoped. There was no contention, no heavy clunk shifts in the automatic, no problems. It was as simple as put the rear in “D” and drive normally
We had originally planned to use an electronically controlled transmission and shift the automatic with an electronic dial mounted on top of the manual shifter. Short story is we found a fully mechanical automatic and went with it due to crunch time.
The only adjustment we could make on this transmission was a cable that links to the throttle cable, the “kick-down” that tells the transmission that you are romping on the gas pedal. Initial tests we left this alone and it shifted at pretty lackadaisically. All we had to do was clamp the kick-down cable out a couple centimeters (pictured below) and our automatic was suddenly a hill climber, shifting somewhere around 5-6k rpm.
I was worried that when we released the throttle pedal (which was linked to both engines’ throttle cables, pictured below) to shift the manual, the automatic would disengage and hunt for the correct gear once we hit the gas again. Not a problem. I suspect because it only senses axle rotation, it was always ready to push just where it left off as soon as our manual shift was complete and we got back on the throttle.
Functionally the auto/manual combo was GREAT! Once you put it in drive you just drove the manual normally. Any place on the track where there was a gear selection question, you were fine with the higher manual gear because the auto was still pushing at the higher RPM. This was very distinct on the hill and in the lower speed corners.
The only problem was minor. The rear “muffler” was extremely loud compared to the front. It drown out the sound of the manual transmission engine. We had to keep a careful eye on the front tachometer for manual shifting. Shifting by sound is pretty instinctive and this took a few laps to get used to. Paul wired in and RPM shift light, but it didn’t work right and it wasn’t a critical problem. Fortunately nobody botched shifting too bad because one engine would be more than happy to push the other way past redline.