[cobra4life]

i am wondering what would be better for all around driving, 3.55 or 3.73 gears. i need to use my 1998 Cobra to get to work, but i also want to use it on the drag strip. what gear would give me pretty good gas milage, but also a lot of power on the strip?

[Julian Moore]

Not much of a difference in rpm at 70mph..maybe 300 rpm. I would go 4.10's, don't fear the gear, will really wake up the modular engine. If no 4.10's I would say 3.73's are the way to go.

[cobra4life]

do you think that 4.10's would be fine for highway driving, or would u go with 3.73's?

[blackfang]

4.30's for a NA motor. Anything less, you are wasting time and money.

[NoSlow5oh]

I would go 4.10's if not 4.30's. Right now I'm in the middle of installing my blower so I'm wating to see traction issues before I change my gears. I will probably be going with 3.73's though. The dohc motors make all their power up top and you need a steep gear to keep them in that range. Going with 4.10's will increase your gas mileage because you can use 5th while crusing in town. My 95 GT with bad oxygen sensors and 4.10's averaged 27mpg on the highway. DONT FEAR THE GEAR!!!!

[h82brag2u]

i would say 4.10 i have a 97 cobra and they made a huge difference it still performes very well on the highway and now has 5th gear power...if you are installing a supercharger i would go with 3.73 or 3.55 but on a n/a cobra 4/10 is the way to go...i have experienced it myself..i am putting a set of 3.55 in it just to see what kind of #'s i can get ...just like to sample things thats all...but the 4.10 will go back in it as soon as i get back from the track...

[h82brag2u]

by the way noslow5oh...........gt's are alot better on gas than cobras to begin with...so its hard to compare fuel economy gt verse cobra about impossible...but your fuel mileage is very common...not disputing that at all...

[2006MustangGT]

Never enough threads on this topic. Here's my experience...

I had a local performance shop install FRPP 3.73 gears for me recently and discovered that the PCM re-flash part is a MAJOR PAIN IN THE YOU KNOW WHAT.

Here are your 2 options:

1. Purchase a Ford Racing Performance Parts (FRPP) kit that includes the Pro-Cal or Pro-Cal II tuner voucher and then tell Ford you have 3.73 gears when you register the product to receive your tuner. The Pro-Cal will require that you tell them beforehand. The Pro-Cal II will allow you to change tire size and axle ratio anytime after you receive the tuner (it's a user adjustable parameter).

2. Purchase an aftermarket tuner (DiabloSport, etc) and modify your current tune to accommodate 3.73 gears in the "axle ratio" menu anytime you like.

NOTE: IF YOU DO NOT BUY A FRPP KIT WITH A PRO-CAL I TUNER AND TELL FORD YOU NEED IT WITH 3.73 GEARS OR IF YOU DON'T GET A PRO-CAL II WHERE YOU CAN CHANGE IT YOURSELF, YOU HAVE NO HOPE OF ALTERING YOUR NON-BULLITT S197 MUSTANG TO ACCOUNT FOR 3.73 GEARS. THE DEALER WILL ONLY BE ABLE TO REFLASH THE PCM TO ACCOUNT FOR TIRE SIZE CHANGES...THAT'S IT! AND FORD WILL NOT SELL YOU A PRO-CAL TUNER BY ITSELF.

I had to learn all this by doing lots of online research and by talking to dealer service centers, part centers, performance shops, and Ford's Performance Group directly. Hopefully, this will save somebody else the headache I had to go through just to upgrade my rear differential gears in my otherwise stock 2006 Mustang GT. Since I had already purchased a DiabloSport tuner/CAI combo it was too late for me to get a Ford tune for my car, which may impact my extended warranty and my ability to sell the vehicle to someone not interested in aftermarket products (DiabloSport tuner now required to remain with the car and the permanent 3.73 gears).

All that being said, I am happy with the performance of the 3.73 gears. They won't make a whopping difference, but they are well-suited for the S197 4.6L V-8 engine and drivetrain. The gears are shorter so the engine revs slightly quicker and higher in each gear. In my opinion, you get more of the engine's useful powerband out of each gear than you do with the stock 3.55s. There is less low-end bog and less downshifting during normal driving. I PERSONALLY WOULD NOT GO WITH 4.10s UNLESS YOU ARE TRULY TRYING TO WIN DRAG RACES AND ARE USING THEM IN CONJUNCTION WITH OTHER MODS. These cars already don't have enough tire grip so it doesn't take much to spin the wheels on street tires and 4.10s would only amplify that problem. Highway driving is fine with 3.73s but I would not go with anything shorter or you will be wasting fuel and revving the engine more than necessary compared to other vehicles on the road. Just my opinion.

[guntek18]

C.F.L.

I didnt see anywhere that it said weather you were driving an "automatic" or a "manual" transed car... I would go with what the majority is saying if it's an auto but, if its manual you want to go with the 373 . thats a kick in the pants feel you want without ruining your highway drivability.

[2oo5GT]

No Cobra's came with an auto unless someone did a swap, but not from Factory.
I would say 4.10's or 4.30's like the rest. the DOHC's power is in the upper band and you need to get it up there.
Good race to point that out....
My 95GT back when it only had a few bolt on's and 3.73's vs. my friends 96 Cobra with bolt ons but stock 3.27's. We went from a roll at 20mph and i probably put about 4-5 car lengths on him. of course by the time we got to about 80mph, he was walking me by a few car lengths.
Like mentioned...don't fear the gear

Heck i have an 2003 Cobra and stock is 3.55 but I have some FRPP 4.10's that are going in after this month.

[gilomach]

410 or 430.some people just keep thinking like in the pushrod era.

[gilomach]

i am a mechanic,and mustangs are very common.all the s197 i have seen have a 3.31 gear set.all you need to do is check the tag on your diff. cover(from factory,i mean).

[gilomach]

if that is ford answer for the added weight,it will be logical to think that if a sn95 performs god with 410's.then the s197 will be alright with 430's.

[gilomach]

another thing is grip.instead of pressing the gas all the way down in first gear,keep the calm,trust your machine,take it out of the hole pressing the gas pedal just enough to spin some tires,get it moving,the rpm's are going to go high fast in first gear anyways.then slam that second with all you got and get ready for the perfect point of shifting to third.i am sure that if you do this you wont have grip problem and the step gears are really going to help you hit the 100 miles per hour mark,seconds before the one with 373's.

[2Manystangs]

Well, I feel keep the stock gears and spray it at the track...that way you can have the best of both worlds...