3.55 and 3.73 gear differences?

[Aftrbrnr]

Before I ramble, I'll say I did a search of the forums on the topic and didn't find adequate information, so this is why I'm asking this question.

Between the above two set of gears, is there significant performance and fuel milelage differences between the two? I've heard 3.73s are the best balance between performance and drivability, but with gas going up, I'm trying to save up as much as possible. Last summer, I would've considered even 4.10s but with gas going up more and more and the fact my car is a daily driver, I'm trying to find a middle ground here.

 

[FrdMustangCpe]

assuming you have a 5-speed it depends on your engine combo to decide btwn the two...i believe. if you have a good amount of hp, i would say get 3.55s and you gain a little more top end than 3.73s. i dont think there is any significant difference, there is some but nothing like 2.73s and 3.73s. yes, you would get a little better mpg w/ 3.55 because when your cruisin your at lower rpm. i have 3.73s and love them, however my plans for my next car, i will get 3.55 because i plan on runnin high hp.

if im wrong please correct me

-Mike

 

[Michael Yount]

It's all about ratios - 3.73/3.55= 1.05 - there's only 5% difference between the two. With 3.55's if you were at 2000 rpm at a certain speed, you'd be at 2100 rpm with the 3.73's. Between average speedo error and tach error you might never know the difference. Flip a coin - they're that close. By the way, the steeper gear may help your in town mileage a bit because less throttle opening will be required to move the car. So even the gas mileage difference is liable to be negligible.

 

[FrdMustangCpe]

Michael Yount....you are the man. i didnt realize that the rpms would be that close together.

 

[notchback]

don't waste your time w/ 3.55's
you will regret you did.
the $1 dollar a day more in gas is well worth it.

 

[_jb_]

If you plan on going with a supercharger anytime soon, get 3.55s. I'm after 3.73's myself right now...and have been forever it seems.

 

[samuraichamploo]

3:55's were the perfect thing for my combo.

 

[hollywood76]

5 spd. go with 3.55's.
Auto go with 3.73's.

 

[PhLoBuS]

going with 4.10s may lose 1 mpg but overall the best gear for your stang

 

[87'GTstang]

I'de have to disagree with that one. These engines put out too much hp to "need" 4.10 gearing. That statement is basically saying why stop there? Go for the 5.36's!!! Seriously I know a few that went with 4.10 and they have too much power - you can't get it to the ground anywhere near as well. So in the end, unless you are running slicks, you'll actually be slower in the quarter because you can practically never floor the damn thing and open it up all the way because of major wheel spin - it's a waste or engine power.

 

[super302]

go 4.10's and never look back.

 

[samuraichamploo]

go 4:10's if your car is slow LOL

If you have some serious power it will just be to much gear.
If I had 4:10's on my car I would def be slower in the 1/4

 

[remat457]

Before I ramble, I'll say I did a search of the forums on the topic and didn't find adequate information, so this is why I'm asking this question.

Between the above two set of gears, is there significant performance and fuel milelage differences between the two? I've heard 3.73s are the best balance between performance and drivability, but with gas going up, I'm trying to save up as much as possible. Last summer, I would've considered even 4.10s but with gas going up more and more and the fact my car is a daily driver, I'm trying to find a middle ground here.

if you drive a lot on the freeway 3.55's...
if you drive in town a lot 3.73's...
and everything everyone has said is true...
You can't go wrong with either!!

 

[PhLoBuS]

a car is never too fast but 4.10s would definetly be the limit, i agree overall the best gears are 3.73s maybe i plan on getting slicks??? =]

 

[timewarped1972]

don't forget to factor in tire height. true you probably would'nt notice much diff between 3.55 and 3.73, but if down the road you get a slightly taller wider rear tire that would also about cancel out the difference if you chose 3.73's......it makes more diff with a stick, with an auto it's kinda a no brainer with 3.73's, plus the nice thing about using 3.73 in an aod is if you decide to ever do a t-5 swap, you wont be over geared....

 

[Venom351R]

going with 4.10s may lose 1 mpg but overall the best gear for your stang

not w/ a supercharger or turbo


3.55's are perfect for my set up

 

[Michael Yount]

The tire height factor works just like the gear ratios - a taller tire is just like putting less gear in; a shorter tire is just like putting more gear in. How much more/less? The ratio of the tire diameters will tell you. Stock Mustang tire is about 26" tall. Let's say you choose 3.55 gears with the stock size tires. Put a tire on it that's 28" tall - 28/26= 1.076. You just cut your rear gear by about 7.5%. So your 3.55's with a 26" tire become 3.30's with a 28" tire. If you were cruising at 2000 rpm with the 26" tire, your cruise rpm would drop to about 1850 rpm.

 

[04sleeper]

As far as the proper gearing is concerned it all depends on what you are going to be doing with the car. If you are looking for optimal gearing for quarter mile performance then you must factor in the engine combination, RPM of the engine, transmission gearing, rear end gearing, and tire height. You should be going through the traps at peak Horse Power RPM or a little above.
The best way to find out your peak Horse Power RPM is on a dyno. Every engine combination is different even if they have the same parts on it. So you can't just go by what someone else is running.

 

[Michael Yount]

Great post by 89sleeper - that also has implications on shift points; most folks shift each gear at the same rpm. However, to get the most work out of the engine, shift points need to be determined based on the rpm at which peak power and torque occur and the tranny gear ratios - shifting so the rpm drops into the peak torque range each time. For T-5's what that usually means is that each shift after the 1-2 should occur at about 200-300 rpm less than the one before. My power peak is at 4900/torque peak at 3800 via dyno data. Optimum shift points for me are 5400 1-2; 5200 2-3; 4900 3-4.

 

[04sleeper]

Thanks Mike! Just trying to keep the bases covered.