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Old 07-07-2016, 10:17 AM   #27 (permalink)
funkhoss
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Join Date: Jun 2010
Location: Henry, VA
Posts: 54

The Little Car - '00 Chevrolet Metro
90 day: 91.08 mpg (US)

The Big Car - '94 Chevrolet Caprice Wagon
90 day: 44.9 mpg (US)
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Quote:
Originally Posted by oldtamiyaphile View Post
Regarding hypermiling and towing, I have the same issue, I do a lot of towing and towing in city traffic, so the ratio choice is always a big compromise. So, I've been thinking about sourcing a two speed (external overdrive) diff like was popular with British cars in the 60's-70's. Most often these could only be engaged in 3rd and 4th, but I don't see why that couldn't be modded out. Two speed diffs these days are still around in some smaller trucks like the Iveco Daily, which might be too big for your use, and the ratios might not suit, but it would be a lot easier than swapping diffs every time you want to tow something.
Yeah, I've thought long and hard about other options, too--such as a Gear Vendors overdrive, a 4WD transfer case with the "transfer" part cut off, or a "Quick Change" rear end out of a race car or hot rod. All three of those options would allow for an easily accessible wider range of gearing. But any one of them would increase the time and expense of the project considerably, and also add a significant amount of extra weight and parasitic drag.

I don't tow that often, so to me the interchangeable axle idea seemed like the best compromise--minimum cost, with maximum efficiency and/or maximum grunt/durability depending on what's needed. But who knows...maybe I'll change my mind in a year or two.
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Last edited by funkhoss; 07-07-2016 at 10:25 AM..
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