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Thread: What gear?

  1. #1
    FEP Super Member NAVYCAT's Avatar
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    Default What gear?

    I will be doing a gear swap soon but what gear should i go with?
    It is a 7.5 rear with the 3.3 I6 with a C4 trans. i drive both street and hwy so really dont care about the gas milage i just want it to get outa the way of semi's when entering the hwy's.
    2017 Ford Explorer Sport (DD) 1986 Capri 5.0 Silver/Red
    1969 Falcon XW GTHO coupe (SOLD) went to Australia
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    3rd. 1984 Capri RS V8 Black/grey
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    1st. 1984 SVO Grey/grey (traded it for a worn out 1970 BOSS 302)
    Both '84 Capri's vin# were 10 away from each other
    U.S. NAVY 1980-2009

  2. #2

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    Whats in there now? I would think maybe 3.73's or 3.90's maybe?
    79 Capri RS
    341 rwhp,348 rwtq 11.20@127


    1939 Pontiac Deluxe 6. 73,xxx original miles. Barn find. Currently the secomd owner.

    2013 Focus ST
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  3. #3
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    Default

    with a 3 speed id say 3.73's

  4. #4
    FEP Super Member mustangxtreme's Avatar
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    Default

    Having ridden in the car, I'd guess it has 2.73s. Joe, while it will be much more fun in town with the lower gears, you may find them too low for the highway. I'd suggest determining the RPMs you will be running at highway speeds for the gear ratios your looking at and then make your choice.
    Dave

    If common sense was common wouldn't it just be sense?

    1983 Capri L T top 5.0 efi aod
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    1981 Black Magic 400 c6
    93 F-250 351 5sp 4x4

  5. #5
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    Its hard to beat a 3.73 for an all around gear.

  6. #6

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    If you have a 26 inch tall tire with 3.73 at 70 mph your rpm would be about 3500, with 3.45 at 70 you would be about 3100 rpm, with 3.27 at 70 it would turn about 3000. I use this calculator to figure stuff like this out http://www.csgnetwork.com/speedcalc.html You may not worry about gas milage but you have to look at wear on the engine too if you're doing a lot of highway driving.To bad you don't have an overdrive then you could go real deep on the gears

  7. #7
    FEP Member 408IIII's Avatar
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    I have 3.73's in my 79 with a c4. I had 4.10's and found it to be too much gear for the highway, even with 28" tall tires. I'm happy with the 3.73's. I'm turning 6100 @ 118.75 on the track with 27" et streets. I also worry about engine wear and I try to keep it below 3000 on the highway. I have a 120 mile round trip to the track.

  8. #8
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    Quote Originally Posted by 1qwkgt View Post
    If you have a 26 inch tall tire with 3.73 at 70 mph your rpm would be about 3500, with 3.45 at 70 you would be about 3100 rpm, with 3.27 at 70 it would turn about 3000. I use this calculator to figure stuff like this out http://www.csgnetwork.com/speedcalc.html You may not worry about gas milage but you have to look at wear on the engine too if you're doing a lot of highway driving.To bad you don't have an overdrive then you could go real deep on the gears
    Good point, I forgot about the no overdrive part. I used to have a 3.55, and it still had pretty good pick up.

  9. #9
    FEP Power Member Hemlock's Avatar
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    Default

    I was also going to say 3.55. The inline six has decent torque and should be able to turn that gear ratio without issue.

    Robert
    1984 RS 347 Capri, To many car parts to list, check out my car build page here for the story on my car and a full parts list/setup!:

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  10. #10
    FEP Power Member black1980fiveoh's Avatar
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    3.55 or 3.73 should make you happy.
    1980 Cobra http://www.cardomain.com/ride/2364382
    11.82@115 mph - 2015 - retired due to cancer
    1981 Cobra
    reborn with a lot of new go fast parts and time to make it look pretty
    11.80 @114 mph - 2016

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