4.10s
 

So as most of you know I've got the 2004 Mach 1. I was about to order some 4.10s for the rear a couple days ago but a guy I work with said that I should get a new trans with an overdrive gear so that I don't burn up my gears. It's got a t3650 trans now with the stock 3.55s in the rear. Is this true? Or could I put 4.10s back there and be fine? Also, what are some opinions in the 3.73s vs 4.10s? I just want more "umph" when I go to the track...

3.73s will give you "umph", 4.10s will give you more.
Never heard of burning up the gears though....

And the 3.73s and 4.10s will decrease my top-end speed right? But help acceleration?

Go with 4.10's or 4.30's...The 4V's really like to rev up and like the 4.30's. Since your car already has 3.55's 3.73's would be a waste of money since you probally wouldnt even feel the increase.

4.30's in a Mach. Your trans will be fine. Top speed doesn't matter. You'll never be going that fast anyway.

4.30's.

I've also heard that they improve your city mpg, is that true?

I have 4.10's and my city mileage is about the same, maybe a little better.

going from 3.27 to 4.10 my city mileage improved from 1.0 - 1.5 mi per gallon. Which is good because that is what the longtubes took away, so i'm pretty much back to what I was getting stock ~ 14.5 mpg.

Why is this in the power adder section? Moving to general tech....

Back to the questions. Whoever told you that doesn't know about modern cars I take it as you already have overdrive just like every other car since what the mid to late 80's. Your tranny will be fine, the rear end will be fine, the motor will be fine. If anything like others are saying I would of gone with more gear if your staying N/A.

Changing to a higher numerical gear ratio will lower top speed. However you will still never be able to go as fast as the top of 5th gear so it does not matter. Your city mpg will normally go up once you stop hitting the throttle alot in the city. Highway mpg will drop slightly normally 1-2 mpg.

i went with 4.10's in my mach, there was a pretty significant difference from the stock 3.55's. but to tell you the truth i do sometimes regret not going with 4.30's.

So right now I'm leaning towards the 4.30s, but regardless wouldn't I need a tuner to set my speedometer for the new gears? Or would the local Ford Service Shop have what they need to reset that?

lol, they probably wont warranty it for sh*t..

Probably not, but they've been good to me in the past.

4.30s would be the best bet in my mind

Bump.

yes you would but it would help with gas and give you a bit more power

you would better off imo getting a tuner, the ford shop might be able to handle it, but with getting the tuner you would have it for future mods.

you can get a tuner or a dallas mustang speed cal.

For my purposes, I think I'll just end up going with the gears and a speedcal. I may eventually end up getting a tuner, but for the amount of money I want to spend, this is more logical.

My car has got really good "get up and go", but I can alway appreciate more. I'm also looking to do some appearance mods before the end of the year or early next year as well. So I want to use my money wisely, considering the future mods I want.

no, that dude is full of it. The one mod I didn't do to my mach when I had it was 4:10 gears and it was a mistake. You have an extra 1,000rpms than 2v-3v cars so 4:10's are perfect. Besides, like everyone else has said, the 4v engine likes and needs to be revved.

Not sure what mods you have now, but add a mid-pipe, cat back, CAI, and custom tune you'll be right at 300rwhp and with 4:10's your be scooting pretty damn good

Current mods are JLT CAI, short-throw shifter, and Magnaflow Performance Exhaust H-pipe

yea i got the speed cal to correct my speedo, If I recall it was like $80???

You are probably on the edge of running lean. The rule with mach's is after 3 mods that bring in more air you need a custom tune. My air/fuel ratio was so dangerously lean when I had a cat back, mid pipe, and CAI. I know it will cost more, but get a custom tune done at a tuning/dyno shop. It will make a difference.

definately

4.30's and hang on. I dont think you will regret done at all. Be safe and save some money for a dyno tune, money well spent. The 3650 already has a overdrive (5th gear) I think its .82 to 1. I dont know where his logic was coming from????