Nighthawk2008

Ok guys, I've been debating this for awhile and still haven't decided which to go with. I have an 08 GT/CS which is my daily driver (for now) and I drive 50/50 highway and city.

I was reading an article in Mustangs & Fast Fords issue May 08 and it said they recommend 4:10 gears in the S197 cars. Said anything less really didn't perk it up enough. But I always get mixed reviews from people saying 3:73 for autos and 4:10 for manuals. Some people say they use 3:73 in autos and wish they had gotten 4:10 and others say 4:10 is too much for an auto. Alot of advice I get is from people who have neither but its on their to do list.

So who I'm interested in hearing from are 05+ mustang drivers with either 3:73 or 4:10 gears who use them for daily drivers in thier automatics. Not interested in those who use them for weekend track use.

Which ever I go with I'm getting them installed next week while I'm off for vacation.

So lets hear from you guys with automatics who have had gears installed.

zkiller

3.73 is the best all-around gear for the automatic. Bigger is not always better and the key factor with gearing is to get one that matches your cars powwer band. If you had a stick and a centrifugal supercharger I'd say go 4.10 for sure.
Also consider tire height. A stock tire height of 27" is good with a 3.73 but if you go to a taller tire, like a 305/45/18 (28.8") it will bring the gear ratio down. So with a 28" tall tire or bigger I would go with a 4.10. I had to go to this size drag radial for traction purposes and now my 3.73 is like a 3.60 gear. If you go to shorter tires the opposite rule would be in effect.

TK07GT

What about 3.90's with an Auto.?

Nighthawk2008

I don't wanna go with 3:90's because I wanna use only FRPP gears and ford doesn't make 3:90's.

wmtheflash

I think you'll find 3.73:1 is going to be the best compromise between mileage and performance. I've had mine for over a year and like them very much.

I haven't paid too much attention to it, but I believe my city mileage might have gone up a bit. Highway mileage is down about 2 mpg. My overall mileage has stayed about the same about 20 mpg. Probably because I do 50/50 driving and picked up a little city mileage.

So, for me, it's been great. Great performance increase without much extra cost.

bodyman

4:10 best bang for your buck! i love the hell outta them!!!!

Sancho805

i thought this logic only applied to V6ers [>:].

since you got a GT, i'd say go for the 4.10s. 3.73s are perfect for me and my style. Plus the 4.0 hits the powerband at about 3500 rpms so 4.10s would have been beyond my preference. GTs hit the the powerband at 4500 i think so the 4.10s will really help get you their sooner and be a nice match.

all depends on your drving style and intentions. if it were me however, i would go 4.10s .

Stangbanger3v

i would say 4.10s for sure

Mikes_BLK_GT

4.10's in the manual are comparable to 3.73's in the auto due to the above mentioned gearing. I am more than happy with my 3.73's and will be better suited for FI.

Nighthawk2008

I don't plan on installing a super charger. The only other performance mods I'll probably do are underdrive pully, motion delete plates and 1 pc drive shaft.

I was wondering since I have a bama tune and had the shift points adjusted, will I have to change them if I go with a lower gear since I'll be running higher RPM's? With a lower rear gear, wont it shift through the gears quicker? I know I'll have to change the tune for the gears but I was wondering if I have to adjust the shift points too?