Quote:
Originally Posted by mpg_numbers_guy
One thing though, is it possible to put in a transmission that is too tall? After all, if it were possible to use taller gearing for increased MPG, wouldn't the manufacturers naturally do that?
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You'll find that in very new vehicles, transmissions have very reasonable top gearing. I want to say the newest Civic with 1.5 turbo motor have a CVT that can cruise as low as 1500rpm at 70mph? Balto would be the one to ask about that though.
It
is possible to go too tall, but it's extremely unlikely you'll find any transmission that bolts up, which is too tall for your motor. You're not going to hurt anything, but you could, in theory, end up with a final gear which is so tall you can't actually maintain speed with it.
In my Insight, the 1.0L 3 cylinder turns around 1700RPM at 55mph, and even at those low revs I can at times see it at less than 50% load while cruising.