DROES99STANG

I have a 99 mustang GT 4.6 SOHC. The aftermarket parts I have installed are the following: BBK Cold Air Intake, Throttle Body Spacer and 2 1/2" American Thunder Flowmaster Exhaust. I am now looking into gears. I don't know if I should get a 3:73, 3:90 or 4:10, I will be doing mostly off the track driving, including street and highway. Part of the reason I don't know what gears to get is because I don't know what I have in there now, I have heard three different ratios, they are: 2:73, 3:08 and 3:27, Do you know wich of these are typically in a 99 automatic mustang gt. Now in the future I do plan on installing a Supercharger, but not for a while. one of my buddies say get 3:73 but my other buddy says definitely get 4:10 because my car is an automatic. I don't understand why I should get a bigger gear just because my car is an automatic and not a manual. Also how does this change my speedometer, how does it throw it off? Now whatever gears you think I should get please tell me how it changes my speedometer for example if I am going 35mph would I actually be going 45 or 25 or however much the gears change it. I am also hearing a Stall converter will help, is this true? and if so what does it do and what would the difference be? Also if you have any other suggestions that are not too costly please share. Thank you!!

yellowgtstang18

get 4.10s and tuner to fix ur speedometer

Stang0005

+1. Be sure to get the tuner because if ur speedo is off then ur milage is going to be off too and its going to show more miles than you actually have.

sprostang

4.10`s and tuner FTW.....

sweet99

I have a '99 automatic, had 3.27's. I bought the ww.rpmoutlet.com tuner and 4.10 combo for $449. with the auto the OD drops the 4.10's to a 2.87 which turns the motor at 2850rpm's at 75mph, fine for cruising and I did not lose gas mlieage. mark

Fallstar01

This is a pretty good setup.
4.10 Mustang Gear kit with Tuner and Gear Oil

Deannostang

'99 through '04 Mustang GT's had 3.27 gears. '05 & '06's have 3.55. If you have an automatic, 4.10 gears are for you. Your year Mustang auto has 4 gears. The '99 GT standard has 5 gears. Doesn't take a genius to figure out what one extra gear can mean to your cars performance. Your entire power curve must maintain itself throughout your 4 (basically 3) gears. Since 4th is an overdrive gear, it is kind of useless as far as true acceleration is concerned. With a standard, you have 5 (basically 4) gears. 5th gear is then your overdrive gear. The 4.10 gears better disperse your power curve throughout one less gear than the standard. 4.10's in a standard can make your first gear kind of tight (fast reving) for some people's taste. Many prefer it that way, however. You preferably do not want to hit your overdrive gear in a quarter mile race. This is not good. Overdrive gears are not designed to be used at WOT (wide open throttle). You can eventually burn out your tranny's overdrive if you consistently do this.

Bottom line, 4.10's you will love with your auto. Buyer beware.....your mileage will go down. All depends on how often you get into it hard. Also, since you will regularly be running your cars engine at an elevated rpm, I suggest a full synthetic oil. I am partial to Royal Purple but most qualtiy full synthetic is far better than any conventional oils out there. Enjoy your ride!

ForeverFord

My wife and I both have 04 gt's. Hers is an auto mines a manual. She travels about 400 rpm's more then me at any giving speed then I do(Fluid drivin). Higher rpm's=parts spinning faster(more wear),more gas used (not much). If you want a fun fast car 4.10's, Funner car but a LITTLE easier on the pocket book 3.73's. Stock gears 3.27's left behind.

Cornbread01

4.10s

DROES99STANG

Ok so after I get the 4:10 gears and I am driving normal, do I have Overdrive on or off. And on the drag I have it off right? When you say OD drops my gear down does that mean I should use OD for regular driving so I don't lose gase mileage? With 4:10's, when I stomp the Gas is it going to be all over the road? also do you know if my 99 gt convertible has full possy stock? or is it slip possy? I don't know much about this whole rear end thing, I am trying to figure it out though, I hope I don't sound like a complete moron. Thanks everyone for your help!!