Just curious why the new Boss would come with 3.73 (yeah for the track!) but the Shelby has 3.31 gears? I know they can be swapped out, just curious as to why they come from the factory setup that way? Any thoughts?
'13 Boss/Shelby 3.73/3.31 why?
- Thread starter beviking
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MoshpitMad
Active Member
Because it has more than enough power, and the longer gearing will help gas mileage for those that use it on the highway also?
LAVAgt2012
Well-Known Member
My thoughts would be that most ppl who purchased the Boss would of been because of it's reputation on the track, and the shelby was more less designed as a high performance street car 
Svtpilot
Founding Member
The articles I read stated that SVT tested various combos of rear end and transmission gear ratios and the 3.31s worked the best. Personally I think the goal of 200+ mph top speed played a big part in the gearing choice. I think they really wanted to hit that number.The 202mph top speed of this car is a big deal, and gives Ford serious bragging rights over Chevy. Besides with 650hp and 600lps of torque I pretty sure the car will pull like a beast regardless of the the gear ratio.
The Boss on the other hand makes most of its power in top and with the high red line can really take advantage of the steeper gears,
The Boss on the other hand makes most of its power in top and with the high red line can really take advantage of the steeper gears,
BackInBlack
5 Year Member
So in your opinion If I only want to end up with just over 400whp in my mustang. cus its a daily driver and road trip car. what gears would be best. I have the stock 3.55 right now
SpartaPerformance
10 Year Member
Ford spent a lot of time calculating the perfect trans gears for acceleration and have 3.31's in the rear to help put power to the ground and maintain decent highway miles.
Svtpilot
Founding Member
I bet it has crazy traction issues with 3.31s, I guess thats why they gave it launch conrol
Ford4me
Active Member
Mine came with 3.73 gears and I love it. I gets decent gas milage and lots of torque.
JKidd
Member
Honestly I feel the 3.73's are the ideal gear for this power level on a daily, street driven car. That being said, 3.55's would be a very close second. If I were you, I'd keep the 3.55's that you have in there. Don't know how much you'd gain going to 3.73's to justify the expense (if you were trying to shave a tenth in the quarter mile and it was THAT important, maybe).
3.55's are a nice gear. I'm sure you can find other areas to spend "gear-swap" money if its burning a hole in your pocket
BackInBlack
5 Year Member
I actually happen to not be into racing the quarter mile. ya it's cool. but I dont mod my car to see how i can do in the quarter mile. I wanna push it beyond those limits. yes, slamming the pedal and seeing how quickly I can max my speedometer but also taking it on long road trips, and breaking my tires loose around turns. I find things more exhilerating without competition.Honestly I feel the 3.73's are the ideal gear for this power level on a daily, street driven car. That being said, 3.55's would be a very close second. If I were you, I'd keep the 3.55's that you have in there. Don't know how much you'd gain going to 3.73's to justify the expense (if you were trying to shave a tenth in the quarter mile and it was THAT important, maybe).
3.55's are a nice gear. I'm sure you can find other areas to spend "gear-swap" money if its burning a hole in your pocket
BackInBlack
5 Year Member
Ive been hearing you lose horsepower with higher ratios but yet you get into the power band faster. do you have any explanations for that.
A lil bit about me is that I just drive cars for the fun. no competition. my reply to jkidd says it all.
Coyote5.0
5 Year Member
It's a physics problem. Shorter ratios usually mean slightly lower numbers on chassis dynos, because on a dyno pull, you are not just accelerating the rollers under the wheels, you are also accelerating the engine. It takes a certain amount of energy to accelerate the engine from its starting RPM to redline. The lower the gear, the faster the engine spins up, meaning the energy it takes to increase the engine speed to a certain RPM is going into the engine in less time. Same amount of energy / less time = more power expended.
In the real world, shorter gearing means better acceleration, though, because shorter gears put more torque on the drive wheels. The torque the wheels experience are the torque the engine has multiplied by the final drive ratio (minus friction losses). The shorter gears trade less distance per revolution for more force.
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