Anyone swap out the 3.8 final for the older, shorter one (cant remember the size) for better highway fuel economy? If so, what was the gain. I have it calculated to drop ~ 325 rpm @ 80mph, so I'd assume maybe 3 mpg gain? I don't know. I'm getting avg 30 mpg right now on mainly highway driving. The only reason I'm considering it is cause I drive roughly 650 miles per week. Just curious to see who's done it and what the gain was. Basically if it's worth it. I'm wanting an LSD as well for the lovely Michigan winters, figured I'd do it all.

Shorter means more gear, as in from 3.73 to 4.10

Taller means less gear, as in from 4.10 to 3.73.

Yes less gear will usually result in increased fuel mileage, but the speedo will need to be recalibrated. Also its possible the processor may need some changes for shift points depending on if it goes off of mph or rpm.

03-04 2.3l cars had a 3.42 final, which id imagine would do something but I havent heard of anyone going down, only up to a 3.82 or 4.06

I swapped out my 3.42(1?) for a 3.82 right before driving to Florida last year and I honestly didn't really notice any difference in my gas mileage. I know that I should have seen some decrease in gas mileage but if it's there it's not very noticeable. My point is that there should be a gain in mpg but probably not a lot. Unless you do the labor yourself I think by the time you source the taller final drive and swap it in it's not going to be worth it from a $$ point of view. It would take a long time to make up that amount of money in mpg savings. That and the pzev gears are loooooooong.

Probably is a 3.41, my bad.

I have a manual trans and a xcal3 so programmings no problem. I would do it myself. I calculate my mpg everytime I fill up, and at three times a week for that matter. IDK, like I said.... I calculated it out to roughly 325rpm difference. So that comes out to roughly 97500 rpm's a week my car won't have to spin, hence less fuel used. I'm sure u didnt notice a mpg difference because ur not driving 1 million miles a week, and checking ur mpg every 15min.