Which Gears Are Best For My Roush Mustang?

427RStangg wants to know: “In my s/c Roush, what gear ratio would you recommend? I have friends who say that 4.10 gears are way too steep for my car? It’s a manual.”

When choosing aftermarket Mustang gears (or any aftermarket mod), it’s important to consider what type of driving you do/want to do with the car, how much power you currently make, and how much power you intend to make.

Aftermarket rear-end gears are designed to get you off the line faster, so you’re going to burn through first gear (and second… and third…) much more quickly than with your stock gears. This isn’t as much of a hassle with an automatic transmission because you aren’t the one shifting, but if your Mustang is a stick and you do any kind of driving in a city or heavy traffic, you’d be wise to avoid the steeper ratios. Considering your pony is already super charged, I would have to side with your friends and recommend the 3.73 gears; they’ll give you the extra kick off the line that you want without making driving a chore.

When installing aftermarket gears, it’s always a good idea to get a bearing kit and replace the shims, bearings, and other items that wear out over time. This will complete your rear-end rebuild and make sure you keep that rubber burning for a long time.

Written by Andrew

"You're telling me it's got four wheels, two seats and goes faster than the speed limit? Good, I'm driving."


  1. hey while we are on the subject, i was wondering what size would be good for my stang its an 03 GT auto with CAI,plenum and throttle body, i dont want to kill gas but i really want to improve acceleration


  2. If I owned an auto, I would go with the 3.73’s as well. I think that they’re a perfect auto gear, no matter what your plans are for the future, Naturally Aspirated or Forced Induction.


  3. No way… 4.10’s for automatic without a doubt. Don’t fear the gear man. Can’t decide then go for the middle man, the 3.90. 4.10’s in an auto will get you into the blowers powerband much quicker.


  4. 03 GT auto here and I put 3.73’s in. Their great. I would recommend those or the 3.90’s, but if you do alot of long driving I’d stay away from the 4.10’s.


  5. I have a 2010 Mustang GT with the track pac option,they come with 373s standard from the factory.I,m installing 456s I don,t do any highway driving and love the get out of the hole feeling these gears will give me.


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