off to drive the before gear vendor mileage check.

[ddp]

I haven't been much of a poster so far, but I just went through the overdrive/mileage project over the last year. Now, I knew going in that it was never going to pay for itself. I just did it to do it and see what would happen.

I have a 71 1/2 ton longbed with a 350/quadrajet that started with a th350 trans and a 3:42 gear set. Next I went to a th350 + 3:08 gear. Then, a 2004r + 3:08. And now, the 2004r + 3:73 gear set. Through all of those combos, I was +/- only about 1 mpg highway. Right now, the overall driveability is the best with the 2004r/3:73 combo. Here's my unscientific results breakdown:

th350/3:42 - 12.5 city, 13.5 highway
th350/3:08 - 12.5 city, 14.5 highway
2004r/3:08 - 12.5 city, 14.5 highway (no lockup)
2004r/3:73 - 12.5 city, 15.5 highway (with lockup)

My city driving is in Chicago, so it's really stop and go, and my highway driving was 65-75 mph interstate over a couple of hundred miles. I always adjusted miles traveled for any error in my speedo/odometer. I'm guessing that I could pick up maybe another 0.5 to 1 mpg if I held the speed down to 65, but..

Anyway, that's been my experience. I guess that at some point it's the aerodynamics (or lack of) that really hold you back.