Rear axle ratio choices

metroplex · Jan 14, 2009

Has anyone swapped in 2.73s for their S197? I can't seem to find any brand new for under $400 a set. I also can't seem to locate numerically lower gears like 2.6x, 2.5x, or 2.4x

Randy 25 · Jan 14, 2009

Seems like you could really lub the engine going to such a high gear ratio. I just bought a new 08 with optional 3.55 gears and so far they seem ideal - of course I'm not tracking it either. They might not even make gears that high for this car......

Randy 25 · Jan 14, 2009

I ment lug the engine, not lub the engine - sorry.

stangzilla100 · Jan 14, 2009

nobody uses those gears. it wont give you any performance whatsoever.

stangzilla100 · Jan 14, 2009

do you mean 3.73?

o0Dan0o · Jan 14, 2009

I've never seen it before. Why do you want the lower gears, better highway mileage? I'm not so convinced that it would help that much.
Dan

metroplex · Jan 14, 2009

I know for a fact that going to 2.73s from 3.55/3.73 on a Crown Vic (4.6L 2V / 4R70W) will result in a gain of up to 10 MPG on the highway, namely because the engine RPMs are kept below 2000 RPM at 80 MPH.

My 07 GT gets about 23-25 MPG on the highway. I would like to see close to 30 MPG and the hit in performance is not an issue. This way I can have both a 300 hp V8 and gas mileage that rivals most 4-banger FWD cars.

o0Dan0o · Jan 14, 2009

Do you have the 3.55's now? My car as the 3.31 and I get pretty close to 30 on the freeway (depending on conditions). At 80 I'm doing 2200 I think, 2.73 would put you at about 1800. That is an 18% reduction in engine speed.
Dan

o0Dan0o · Jan 14, 2009

What mods do you have? With mine I gained roughly 5 mpg highway.
Dan

klaw · Jan 14, 2009

metroplex said:
I know for a fact that going to 2.73s from 3.55/3.73 on a Crown Vic (4.6L 2V / 4R70W) will result in a gain of up to 10 MPG on the highway, namely because the engine RPMs are kept below 2000 RPM at 80 MPH.

My 07 GT gets about 23-25 MPG on the highway. I would like to see close to 30 MPG and the hit in performance is not an issue. This way I can have both a 300 hp V8 and gas mileage that rivals most 4-banger FWD cars.

You could probably back off the tune as well. So say with a tuner and new gears, you would have spent $1500 to turn your V-8 into the mileage and performance of a 4 banger. At current gas prices, how many miles do you need to drive at the increased fuel economy to pay out the investment in the tuner and gears? I'm struggling to see the rationale for what you're doing. You bought a performance car to try to turn it into a fuel economy project?

metroplex · Jan 14, 2009

I have the 3.55s now but I wish I didn't opt for them so I could stick with the 3.31s. I just saw "Limited Slip 3.55" and wanted to make damn sure I got a limited slip. Ford screwed me over big time by not making a LSD optional or standard on the Crown Vic.

It seems the 3.31s would work well, but I'd imagine the 2.73s would give an even higher boost in fuel economy. Plus there'd be less shifting in the 1/4 mile and 0-60 MPH tests.

stangzilla100 · Jan 14, 2009

with gears that short, off the line you'll be slow. i never have my rpms below 2000, the engine is straining to have any accelleration w/ that low of rpm's. and if you do run the 1/4 mile or do a 0-60 test it's gonna suck. i hate to be a hater on your thread, but my mazda doesnt even get 25 mpgs , and my GT gets 12-13 mpgs, but that's ok w/ me i didnt get the GT for mpgs anyways. if you do put in 2.73's you can forget about the 1/4 mile bc it wont even be worth it to run down the track. having to shift later isnt a plus, its a minus bc you're accellerating slower, i.e. trap speed will be down. sure you'll have better economy, but performance will be worse.

metroplex · Jan 14, 2009

Well I always shift at or below 2k RPM with my GT, and I frequently lug the engine around the city. I never understood why people NEED to run the engine at 3000+ RPM with a manual.

retfr8flyr · Jan 14, 2009

The lowest you will find new are 3.08 ratio you can get them here Ford Racing M-4209-F308 - Ford Racing Ring and Pinion Sets - summitracing.com

Earl

08blueskunk · Jan 14, 2009

whats the point of having the 300Hp with such low gears, you might as well have the 4 banger,

a civic will beat you off the line with 2.73 (maybe)

DarkFireGT · Jan 14, 2009

stangzilla100 said:
with gears that short, off the line you'll be slow. i never have my rpms below 2000, the engine is straining to have any accelleration w/ that low of rpm's. and if you do run the 1/4 mile or do a 0-60 test it's gonna suck. i hate to be a hater on your thread, but my mazda doesnt even get 25 mpgs , and my GT gets 12-13 mpgs, but that's ok w/ me i didnt get the GT for mpgs anyways. if you do put in 2.73's you can forget about the 1/4 mile bc it wont even be worth it to run down the track. having to shift later isnt a plus, its a minus bc you're accellerating slower, i.e. trap speed will be down. sure you'll have better economy, but performance will be worse.

Actually, those gears that (numerically) lower would be taller gears. Shorter gears would be moving up to 3.73 or 4.10.

Honestly, with a better tune, you'll be where you want to be. Hit up Doug@Bamachips and tell him that you need a tune for best gas mileage and he'll set you up properly. Running the 93 Race tune, I see around 22 city, 27 interstate, and up to 33 highway with 3.31's. You have lower gears, but if you had a tune optimized for gas mileage, you could definitely surpass those numbers.

My Magnum R/T had 2.82 gears and it wouldn't get out of the hole to save it's life. Granted, it was a heavier car. But even with the lower gears and variable displacement system, the best I ever saw out of it was 27MPG@50MPH.

Yes, on the highway, you may get some good gas mileage, but it'll take more fuel to get up to speed. Just get yourself a tune specifically tuned for gas mileage, and you'll see what you're looking for, without turning your car into a slug.

stangzilla100 · Jan 14, 2009

DarkFireGT said:
Actually, those gears that (numerically) lower would be taller gears. Shorter gears would be moving up to 3.73 or 4.10.

sorry, my english is all backazzwards. but you know what i mean.

when cruising, i shift at 2500 rpms at the least. i think shifting below 2000 rpms hurts your engine and possibly your mpgs as well. when you shift that low you need more fuel to get going when you shift to the next gear, but when you take it up above 2000 rpms you dont have to throttle as much. does that sound right?

MustangGT08 · Jan 14, 2009

Why kill performance? Sub 3.00s will yield a slug off the line, and in-town MPG will suck. A good CAI and tune with exhaust mods will get you to near 20 mpg town, near 30 mpg hiway. I am doing it with my '08, and performance is very good.

mustangford289 · Jan 14, 2009

Jike?

metroplex said:
Well I always shift at or below 2k RPM with my GT, and I frequently lug the engine around the city. I never understood why people NEED to run the engine at 3000+ RPM with a manual.

Is this guy joking? I am LMAO!!!

mustangford289 · Jan 14, 2009

LOL not jike but Joke?

A little correction for the title of my previous post...

Rear axle ratio choices

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