gils maui pony

I'm going to add gears to my car.yeah!...now, has anyone driven two automatic mustangs with the 3.31 and the 4.10?...with the auto coming out with 3.31 and standard 3.55, does that mean installing 3.90 in an auto would be comperable to having a standard with 4.10?

MUSTANGGT06

Go on the web and look up "Alternative Auto Performance" out of Michigan. In their opinion, putting 410's gears in the new automatic 05 and up Mustangs is a waste of time because of the gear ratio in the new 5 speed automatics. Something about the gears being to steep. I'm not a mechanic, so I don't what to tell you what to do. However, I just installed 4.10's in my automatic thinking I was going to see big gains in my Et's (specially 0-60 ft) and I haven't.

Nuke

I'm not sure about the auto's having steeper gears and my files are on another computer that's not hooked up yet but I believe that's correct. However, since I'm feeling ornery today, I thought I might start a little tiff by being a "tranny bigot" and say that auto drivers don't know how to drive so they're given lower gears as compared to us manual guys that KNOW how to drive and can handle it.

But honestly, i DO believe it's the ratio differences between the auto and manual.

mustangtestuser

It's because of the difference in transmission...

Final drive = transmission gear ratio X differential ratio. It's different for each gear. So, for first gear for example:

Automatic
1st gear 3.22:1
Differential 3.31:1

3.22 X 3.31 = 10.66:1

Manual
1st gear = 3.38:1
Differential = 3.55:1
3.38 X 3.55 = 11.99:1

To find out the ratio for each gear you repeat the process for 2nd, 3rd, 4th, and 5th (overdrive). The most important gear in terms of daily driving (in my opinion) is overdrive, since that's the gear you'll be using on the highway. It's .75:1 in an automatic and .68:1 in a manual. So:

Automatic 5th gear, 3.31:1 differential = 2.48:1
Manual 5th gear, 3.55:1 differential = 2.41:1

Essentially equal. That's also why Ford Racing recommends 3.73:1 for an auto and 4.10:1 for a manual.

Automatic 5th gear, 3.73:1 differential = 2.80:1
Manual 5th gear, 4.10:1 differential = 2.79:1

In the last generation Mustang the situation is reversed. In that case, the auto has the more aggressive overdrive gear, so Ford recommends 3.73:1 manual and 4.10:1 auto for 99-04.

tdbrown75

I have an auto in my Mustang but wager I could outdrive you with either transmission. ;-)

Tim

Nuke

A 3 legged dog could beat me off the line. So what's your point? LOL!

tdbrown75

Well I only two.... that's why the auto!

Tim