That probably makes the most sense out of anything. It would up the mileage (if driven correctly), and allow either drivetrain to freewheel and weigh less overall. Technically its not carb legal unless the engine/transmission is swapped, but if I put a M/T ecu in I don't see how they could argue. My front transmission is at 292k miles - maybe if something goes awry, it would be a good time to do that. Right now I have independent shifters, and this would become yet another machining project with a M/T. But it would definitely be trivial compared to some of the other projects.
The auto is nice for a lazy driver and only does ~3000 rpm at 65-70, and its 1-2 gears are nicely spaced for acceleration, but it almost needs a high overdrive gear for cruising, and a more tightly spaced 3-4 gear. Many newer cars do mid-low 2k rpms on the fwy, Ive noticed. Trouble is torque drops off sharply below 2500 rpm, so very high gearing might not be beneficial. Transmission loss is usually proportional to load, so dividing the load by two shouldn't yield more net power loss, but in an automatic the slippage is decreased by more than a factor of two for a given load. So the question is where is the loss in efficiency coming from? My guess is that its a combination of the pumping loss, driving style, and more heat loss than a similar displacement v6. But its by no means half of a single engine! I'm still interested to see how much the vacuum goes up when both are running.
no offence, but you really are over complicating the explanation to stay with automatics. D series manual transmissions are abundant, cheap, and have a wide array of gear ratios and final drives. Period. Clutches are inexpensive.
the most complicated part... and it isn't complicated, is fabricating the shift linkage for the rear transmission. I'd put both stabilizer bars on high durometer bushings, (and make sure your engine mounts are similar) leave the front shift rod stock as is, fab a adjustable bell crank to reverse actuation for the rear shift rod and pivot it of of a multitude of mounting locations off the back side of the block and or transmission case. Twin clutch MC's and you're pretty much good to go.
Honestly, probably the simplest thing yet on this project car. Turbos and a better IMEP later. I'd say...... keep it simple...... but after looking at the throttle pedal i'd say you're well beyond that.
D ~ thanks for the input. I was agreeing actually, but I need to wait for a reason to swap the transmissions first, for instance when one breaks. This is on the ultimate to-do list sometime in the future - probably a 5 speed would be best.
Comments
The auto is nice for a lazy driver and only does ~3000 rpm at 65-70, and its 1-2 gears are nicely spaced for acceleration, but it almost needs a high overdrive gear for cruising, and a more tightly spaced 3-4 gear. Many newer cars do mid-low 2k rpms on the fwy, Ive noticed. Trouble is torque drops off sharply below 2500 rpm, so very high gearing might not be beneficial. Transmission loss is usually proportional to load, so dividing the load by two shouldn't yield more net power loss, but in an automatic the slippage is decreased by more than a factor of two for a given load. So the question is where is the loss in efficiency coming from? My guess is that its a combination of the pumping loss, driving style, and more heat loss than a similar displacement v6. But its by no means half of a single engine! I'm still interested to see how much the vacuum goes up when both are running.
the most complicated part... and it isn't complicated, is fabricating the shift linkage for the rear transmission. I'd put both stabilizer bars on high durometer bushings, (and make sure your engine mounts are similar) leave the front shift rod stock as is, fab a adjustable bell crank to reverse actuation for the rear shift rod and pivot it of of a multitude of mounting locations off the back side of the block and or transmission case. Twin clutch MC's and you're pretty much good to go.
Honestly, probably the simplest thing yet on this project car. Turbos and a better IMEP later. I'd say...... keep it simple...... but after looking at the throttle pedal i'd say you're well beyond that.
Best of luck.
D