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Thread: Gear choices

  1. #1

    Default Gear choices

    Since its been forever owning a fox body I have a choice coming up for a gear ratio.
    The car has a mildy built 302 with a fairly healthy cam. World class T5 and for now 16 rims. The 3.73 rear end was WAY too tall for my liking and the motor has enough grunt to pull a tall gear. Down the road it will only be higher HP as I built the car out. I have a good set of 2.73s laying around but they may be too low. I'm thinking 3.27 might be a good choice for me, or even a 3.08?

    Car will do everything. Cruise, open track day, once a year 1/4 mile and auto cross from time to time. At some point an 18 " tire rim set up will go on so tire will get taller. Any opinions??? Yes I know that's a dangerous ask on a forum.

    Sent from my SAMSUNG-SM-G890A using Tapatalk

  2. #2
    FEP Super Member 84StangSVT's Avatar
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    I'm running a 3.27 gear in my 84 GT and it suits my driving needs just fine. Even with that gear, it pulls good from a stop and I have no issue getting where I need in a hurry. I don't race it, but I do a lot of interstate driving and the gear helps with that. I run around 2100 at 75 mph with the 5.0 and 5 speed.
    Brock
    1984 Mustang LX Convertible 3.8L V-6/Auto (SOLD)
    1984 Mustang GT Hatchback 5.0 V-8/5 Speed

    I'm an FEP Supporter and proud of it. Are you?

  3. #3
    FEP Super Member gr79's Avatar
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    My stock 85 LTD LX had 3.27. Would have been more fun with 3.55+ off the lights.
    3.73 may be too much now, but a tire change or engine hp build later may need it.
    3.27 is about -50 from 3.73

    Like 2.73 vs 3.27, 3.55 to 4.10
    3.55 is a change, may be fine later or even now. Not a huge change, but may be where it should have been/be.
    3.27 may be fine for you now. Later??? Depends on how you want to drive the car.
    A ton of torque makes rear gear less of an issue. Horsepower engine needs revs to be driveable (hot cam, etc).

    Overdrives have made lower gears more practical.
    Assuming v8 T5 5th is .70 (ratio) of 4th:
    3.55 x .70= 2.48 final
    3.73 x .70= 2.61
    3.27 x .70= 2.28
    4.10 x .70= 2.87
    2.73 x .70= 1.91
    How does car feel in 5th gear?

    Driving a 2.3T, there are times i wish i had a 3.73 or 4.10 gear back there.
    Fuel econ is not a real issue. steady 20+ no matter what.
    V8's have a much wider swing low to high mpg.
    The 2.3 likes rpm, more so than most 5.0's. Has good torque, but much less than a v8.
    5.0 can stay in the 1000-2000 most of the time regular driving.
    2.3T likes 2000-3000, although its fine with 1300-2000 slow street driving.
    3.73 for freeway for sure, 5th gear, 62-65 mph.
    3.45 seems too tall 55+ mph.
    4.10 for cruise nights.
    Most of the time, 3.45 is ok. No way 3.27 with a 4 cyl.

    Gearing slang:
    3.73= short, lower than 2.73
    2.73= tall, higher than 3.73

    http://www.hotrod.com/articles/how-gear-works/

    Depends on how one uses the car. Everyday economy, towing, or race ready.
    Assuming stock V8, no overdrive, stock dia tires.
    Brochures listed optional gears.
    The higher the number (lower rear gear). Two identical cars? lower rear= faster car,
    Economy = 2's, low 3's. 2.79, 3.00, 3.08
    Better performance, 3.23, 3.27, 3.42, 3.45
    Street/tow/strip = mid 3's, 3.55
    Street/strip performance= 3.73, 3.91
    Max performance= 4.10, 4.56 gas suckers.

    Stock 69-70 Chevelle SS 396/4sp w/3.55 driving feel is just right. The halfway point of street/strip gearing.

    Small engines need more gear for pulling weight or speed.
    Larger engines benefit from more gear for pulling or speed.
    Torque motors get away with less gear (lower number). Horsepower engines need higher numbers.

    For good overall daily economy and fun drive ability, need gears that keeps engine in max torque range.
    Racing gears (3.91+) with higher rpms help keep engine near hp curve, but less fun to drive non strip.
    Watch the stock older non od big engine cars on the way to a cruise on the eway. 50-60, 3000 rpm.

    Tire dia, curb weight, engine displacement and configuration, trans, all are factors to find were the car is fun to drive.

    One way to find out how the car would be like with a certain gear is to try different tire diameters.
    Not easy to do, changing, borrowing tires. Changing rears is expensive too.
    Or drive a similar car with the gear you want.

    http://www.4lo.com/4LoCalc.htm

  4. #4
    FEP Super Member cb84capri's Avatar
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    Get used to the 3.73 and stick with it for now. It's a good all around gear right now, and the car isn't going to launch at the strip on a sticky tire n/a with numerically lower gears.

    Cale

  5. #5

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    Quote Originally Posted by gr79 View Post
    My stock 85 LTD LX had 3.27. Would have been more fun with 3.55+ off the lights.
    3.73 may be too much now, but a tire change or engine hp build later may need it.
    3.27 is about -50 from 3.73

    Like 2.73 vs 3.27, 3.55 to 4.10
    3.55 is a change, may be fine later or even now. Not a huge change, but may be where it should have been/be.
    3.27 may be fine for you now. Later??? Depends on how you want to drive the car.
    A ton of torque makes rear gear less of an issue. Horsepower engine needs revs to be driveable (hot cam, etc).

    Overdrives have made lower gears more practical.
    Assuming v8 T5 5th is .70 (ratio) of 4th:
    3.55 x .70= 2.48 final
    3.73 x .70= 2.61
    3.27 x .70= 2.28
    4.10 x .70= 2.87
    2.73 x .70= 1.91
    How does car feel in 5th gear?

    Driving a 2.3T, there are times i wish i had a 3.73 or 4.10 gear back there.
    Fuel econ is not a real issue. steady 20+ no matter what.
    V8's have a much wider swing low to high mpg.
    The 2.3 likes rpm, more so than most 5.0's. Has good torque, but much less than a v8.
    5.0 can stay in the 1000-2000 most of the time regular driving.
    2.3T likes 2000-3000, although its fine with 1300-2000 slow street driving.
    3.73 for freeway for sure, 5th gear, 62-65 mph.
    3.45 seems too tall 55+ mph.
    4.10 for cruise nights.
    Most of the time, 3.45 is ok. No way 3.27 with a 4 cyl.

    Gearing slang:
    3.73= short, lower than 2.73
    2.73= tall, higher than 3.73

    http://www.hotrod.com/articles/how-gear-works/

    Depends on how one uses the car. Everyday economy, towing, or race ready.
    Assuming stock V8, no overdrive, stock dia tires.
    Brochures listed optional gears.
    The higher the number (lower rear gear). Two identical cars? lower rear= faster car,
    Economy = 2's, low 3's. 2.79, 3.00, 3.08
    Better performance, 3.23, 3.27, 3.42, 3.45
    Street/tow/strip = mid 3's, 3.55
    Street/strip performance= 3.73, 3.91
    Max performance= 4.10, 4.56 gas suckers.

    Stock 69-70 Chevelle SS 396/4sp w/3.55 driving feel is just right. The halfway point of street/strip gearing.

    Small engines need more gear for pulling weight or speed.
    Larger engines benefit from more gear for pulling or speed.
    Torque motors get away with less gear (lower number). Horsepower engines need higher numbers.

    For good overall daily economy and fun drive ability, need gears that keeps engine in max torque range.
    Racing gears (3.91+) with higher rpms help keep engine near hp curve, but less fun to drive non strip.
    Watch the stock older non od big engine cars on the way to a cruise on the eway. 50-60, 3000 rpm.

    Tire dia, curb weight, engine displacement and configuration, trans, all are factors to find were the car is fun to drive.

    One way to find out how the car would be like with a certain gear is to try different tire diameters.
    Not easy to do, changing, borrowing tires. Changing rears is expensive too.
    Or drive a similar car with the gear you want.

    http://www.4lo.com/4LoCalc.htm
    Wow, thanks for the info

    Sent from my SAMSUNG-SM-G890A using Tapatalk

  6. #6

    Default

    In my 60k '85, I had stock 2.73. Went to an 8.8 with 3.08 when I upgraded the brakes to rear disc aero front brakes. Then I installed 3.55's. I turn 2k at 65 mph.

    My car is a t-top cruiser. I kind of wish I had gone 3.73.

    I ordered my jeep with 3.73. Also a stick

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