Automatic 2-1 rough downshifting

wstar

Are you coming to a stop soon? Are you coming up on a corner? What's the min speed you intend to hit in the corner? Are you accelerating slowly right now for a few seconds (someone's in the way), but about to get on the gas right afterwards (there's an opening in another lane a few seconds away)? Are you accelerating hard right now, but intending to drop back off the gas considerably once you reach XX mph?

All of these sorts of things and countless others go through your head picking your current gear manually. An automatic transmission in D-mode really only has three basic input variables to work with for making a gearing decision for you: Current Vehicle Speed, Current Engine RPM, and Accelerator Pedal Position. That's true of any auto transmission, even on a minivan.

If your tranny can't make up its mind and settle on a gear, it's because your inputs (the 3 above) are fluctuating in patterns that don't make sense for what it's designed for. It can't possibly know all of the other factors in play. For everyday poking around in traffic, an automatic transmission makes reasonable gearing decisions for average drivers, focusing mostly on fuel economy, and trying to respond quickly with a downshift if you stomp the gas pedal hard to pass someone.

It should come as no surprise, especially in more complex situations, that an auto transmission makes poor or even schizophrenic gearing decisions. Use the M-mode, Luke.

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