Thread: Some contemplations on overdrive

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Well, probably would be better, but you would also have to totally redesign the differential. to be a 1:1 ratio the ring and pinion would have the same number of teeth, that's not going to work (mechanically speaking) in the rear end design we have now... I don't have any idea what the amount of drag is when in overdrive, but the new 5 and 6speed transmissions are well designed and I'm sure it's minimal loss.

Best case scenario would be a constantly changing drive ratio and no gears similar in theory to the way a snowmobile drive works. Think Chrysler tried this in the 50's. Perhaps replace the transmission as we know it with a hydraulic pump and drive assembly that would have a constantly changing drive ratio based on the power demanded to accelerate to or maintain a given speed??????

Dave, I didn't mean a 1:1 differential, I meant a 1:1 top gear in the transmission instead of overdrive.
The constant variable transmission like a snowmobile is a great idea and I have that rattling around in my brain too. I read about a guy who used a 17 horse Kubota in a 1200 pound car like an old triumph or something. He kept the 5 speed and clutch somehow. Around town he just left it in 3rd and got 67 mpg and 100 mpg highway. The whole theory there is it takes a much smaller engine to maintain cruise than it does to accelerate. Plus a constant engine speed is much better too.
Subaru did have it in the Justy too but I don't think there is anything like that for a pickup or larger vehicle.