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Zoranan 03-21-2013 12:27 PM

3.73 gears effect on gas milage?
Hey guys, I am planning on doing the 8.8 swap on my 1998 V6, and originally I planned on putting 3.73 gears in the 8.8 rear end before I installed it on my car, however my car is a daily driver and I want to know how badly these gears will affect my MPG. Maybe I should do the 3.55's or just stick with the stock 3.27's that are in the GT rear end?

Let me know what you guys think, I want to improve acceleration without hurting gas mileage too badly

P4452 03-21-2013 02:50 PM

I found the 3.27's in the GT rear I picked up to fit my V6 auto quite nicely. No figures on MPG, as this is not a car I drive often.

Lower gears (3.73, 4.10, etc.) will, generally, give you better city mileage. Taller gears (2.73, 3.08, etc.) will, generally, give you better highway mileage. 3.27 and 3.55 are middle-of-the-range.

The lower gears basically reduce engine load, making the same amount of torque act like more torque(requires less throttle to accelerate at the same rate). The taller gears do the opposite, but the reduction in engine RPMs reduces friction at cruising speeds.

If it's worth any comparison, I have a Scangauge II I use to track MPG, mostly in my GT. At 30 MPH cruising in 3rd gear it tends to score around 17 MPG. When I shift to 4th and hold 30 MPH it scores 24 MPG. The difference between the gears is 33%(1.33 vs 1).

The difference between 2.73 and 3.27 is about 20%(3.27/2.73). Going from 2.73 to 3.73 is roughly 37%. Remember, though: that's a 20 or 37% increase in torque at a certain vehicle speed, but it's also a 20 or 37% increase in engine RPM at the same vehicle speed.

2Manystangs 03-21-2013 03:16 PM

milage mostly depends on how fast you drive, plain and with 3.73s you may find yourself "getting on it" alot more, however the fun factor is well worth the very slight reduction in mpgs

Zoranan 03-21-2013 05:40 PM

Well I do drive this in town mostly, but I will be driving highway as well. I think for now I might just get the gt rear and bolt it up without changing gears to see how I like it. Worst case I swap them later i guess. I'm upgrading slowly as I get the money.

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