Honda Automatics with '2' as the last gear position
This probably applies to other vehicles, but I can only speak definitely on older Honda automatics based on my personal experience. I have been playing around with it a bit lately when I drive my grandmother's '90 Civic LX automatic...which I'm doing much more often because I can beat the fuel economy of Mazda3 with manual transmission by up to 10 mpg! Then again, Zoom-Zoom most definitely isn't part of the 18-year old, 92hp Civic's repertoire.
In this '90 Civic, the automatic transmission has shifter detents/gear indicators for D4, D3 and 2. D4 is the position that allows normal operation with the transmission starting in 1st gear and shifting to 2nd, 3rd then into 4th gear (overdrive). The D3 position operates the same as D4 except it locks out the 4th gear and shifts no higher than 3rd. The '2' position seems like it would probably just allow the 1st to 2nd shift and go no higher.
Actually, '2' is just as simple as it as it appears- it locks the transmission in 2nd gear- meaning it can't access 1st, 3rd or 4th! Starting from a stop in the '2' position has actually improved my fuel economy by about 2mpg over the last 200 miles that I've been playing with it. The already pokey Civic makes very slow progress initially in 2nd, but if traffic permits I'm fine with that. Then, when I reach an engine speed where the transmission would upshift to 3rd, I go ahead and slide it up into the D4 position for normal driving. This car has a tendency to hold 1st gear to at least 4500rpm if you start out in D3/D4 unless you use feather-light pressure on the accelerator. Staring in 2 saves the gas used running to 4500 rpm and keeps most shifts down around 2500rpm.
I'm not sure how never model Honda automatic transmissoins function in '2', but I have noticed that more recent models also have a '1' slow below the '2'. But on Civics, Accords and Preludes that have '2' as the lowest gear positions.....this trick can work.
Behavior varies from vehicle to vehicle. Some start in 2, some start in 1 and just don't exceed 2 (unless you redline).
Keep in mind that you're thrashing the transmission fluid in the torque converter a little bit. It shouldn't be a problem, IMO, just check it regularly and be sure to change it according to schedule or a little sooner.
That's a snow gear start-off. Honda designed the transmission to start in second gear so in slippery conditions you could allow for a softer start by slipping the converter. I think it's a great observation on your part to utilize this as a mileage improving tactic. The snow gear is not a new concept, as you observed, Ford used it on thier C4 transmissions back in the '60s. However, I agree with theholycow, you are spanking that fluid pretty good.
A torqueflite derived transmission (Chrysler 3 speed) has D, 2, 1. It behaves approximately like this.
In D it will upshift early at less than 50% throttle, dependant on pedal pressure, kicks down at around 75% throttle, and downshifts as late as possible when coasting. 2 it will upshift later and downshift earlier. 1 it goes to redline in every gear before it will shift, regardless of throttle opening, and will only shift down near the point of engine stall. Typically 2 is seen as "engine braking" gear for descending steep passes.
No snow gear there, but 1st gear is about the same ratio as 2nd on most manuals. If you're thinking in terms of a manual box, it's like it's got 2nd 3rd and 5th.
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