Gear ratio - Gas milage VS Performance

Whoever is wondering why they get bad gas mileage at 75-80 MPH is becuase the wind resistance. If you go 70, which is 5 over my freeway limits, i can get about 24mpg with 4.10's. And the wind resistance difference between 70 and 80 mph is a lot, thus you get worse mileage becuase the car is actually being pushed(held) back by the air.


Ill put it this way. go atleast two gear ratio steps above what your car has stock or you will sorely dissappointed.

I went from 3.31 to 4.10 in my manual and think it is just right.

3.73 is not enough gear for a manual tranny 05+ stang unless you are boosted IMO.

What about if you plan on going with N2O? Would 4.10's be too much?

This is what I did in my automatic and very glad I did. Infact on my 31 mile commute home from work this evening I drove it in 4th the whole way. It tacked at no lower than 3500 RPM and as high as 5000 RPM. The response of the throttle and the sound of my exhaust leaves me

Just one more question. What are the chances that installing the gears will mess something up in my car? Also if something does happen, can ford tell that there were gears installed just by lifting it and looking at the underside? If they can tell, could they tell that i had 4:10's then reinstalled the 3:31's before bringing the car in for service?

visually you cannot tell. if they rotate the tire and count the revs, they can tell. if you swapped the 3.31s back in, it would be difficult to prove 4.10s were ever in there.

if the install is performed properly, there should be no issues with a gear swap.

Can someone tell me what my rpm's will run @ 50, 60, 70, 80, and 90 with 4:10s and 3:37s. I bought the 4:10s but havent installed them yet because im SCARED AND CONFUSED!

Go with the 4.10s, I wish I did, for more details on that go to the "373 intallation with no tune...any troubles?" thread. My speedo is not acurate after the swap to 3.73s but I am pretty sure that I am right at 2000rpm in fifth gear at 70mph. That is with a manual and 18" wheels, other setups might be different. This motor needs to rev, don't be scared, I was and now I am sick

With 4.10s, 235/50-18 OEM tires and automatic I run 2400 RPM @ 70 MPH and 3000 RPM @ 80 MPH in O/D while still being able to pull 19-24 MPG. I love it

unless you're a traveling salesman, dont let the highway issue dissuade you from getting 4:10s. i have a manual w/ 4:10s and cruising at higway speeds i think it tachs out somewhere between3000-3200rpms. in the city first gear is pretty much useless, unless someone pulls next to you w/ that look in their eyes. but since you have a auto, i think you will be more than happy with 4:10s.

so for a manual gt that goes 14-15 miles straight through the city and about 60 traffic lights one way, 5 days a week, would i be killing myself shifting by going from the 3.31's to the 4.10's?

Not at all. Same amount of shifts, you'd just be running higher RPMs. Think of it this way...you wouldn't be getting as much carbon builup Plus your exhaust note will be more pleasurable. I know mine sure sounds better being higher revving.

ALRIGHT ALREADY! I took the plung. My 4:10's are being installed as I type. Now, before I go pick up my beast, I need to know if there is a wear in period or can I go lay down some pin striping on the road ways of the great state of Florida.

you are going to get all sorts of replies on this one. basically, nobody agrees with anyone else on proper break in. some say to rip on it from day one, some say to vary rpm for the first 500 miles, some have a heat cycle to follow, etc.

since you had someone install the gears for you, ASK THE INSTALLER. he will be providing the warranty on his work, so follow his (or her) advice. that way, it wont come back to bite you in the butt later if an issue arises.

Well, I got the gears and I have some questions, concerns, and complaints. 1st I bought a shim and bearing kit with my gears but the autoshop guy said that he wasnt able to use the shims because it was too tight and he had no room to use them. I thought that using shims were a must! 2nd I do like my new gears but my rear end now growls at me. Also there seems to be a whistleing noise back there when I let the motor rev down. the tech said that the gears will heat up then shrink when they cool. is that bs, is he trying to pull one on me or, is this true?

The guy who put mine in had to use different(non factory)shims. He tries reusing the factory ones by flipping them around backwards as to how they came out of the car(sometimes he says it works, so that is why he tries that first). Your new gears should not make any more noise than the factory installed gears...period! If he got the gear meshing pattern correct, the backlash within spec and friction modifier then you should be a-ok. I would definitely take it back to him and have him check those. The guys at the shop that did mine just laughed at me when I asked if they used the friction modifier! The guy working on my car just pointed over to a shelf as he was taking the rear apart and said they order it by the case! I was standing there the whole time so I did infact witness it going into mine. Once the work was done and she was back on the ground, they said if there are any noises or clunks in the driveline to give them a call immediately and drive/tow it back to them and they'll fix it! Now as far as break in, I second bigcat's advice as to asking the person installing them as to what you should and should not do.
Good luck!

Thanks guys.