for those who can't decide 3.55 vs 3.73

Discussion in 'Fox 5.0 Mustang Tech' started by remat457, Jul 29, 2004.


  1. CobraGT87

    CobraGT87 Mr. Speed Density Founding Member

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    I got talked out of 3.73's a few years back by a local mustang shop. The guy said just about all the street stangs around ran 3.55's. so I went with them (although I went there for 3.73's but got talked out of it :bang: ).
    Ran the 55's for about 6 months or so and with a fairly mild 302 at the time, they felt OK but not that big of a deal over the 3.08's. It deff felt like it could of used more gear. mileage was decent, but due to installer error, the gears started to howl. long story short, got the entire rear guts replaced free of charge and this time had 3.73's put in. mileage picked up by 2mpg city & 3-4mpg freeway and just a far more fun & enjoyable car to drive.

    IMO, for the approx 150 rpm diff between the 2 sizes in 5th at 70 mph, 3.73's are are a far better all around gear for a mild-moderate 302-306. I just wish they made the 3.90's back then :bang: With the 347 I have now, the 73's make very nice use of the TQ this motors makes and wouldn't want any other gear size for the street. They feel great even when N20 is used.

    Just my $.02
    Scott
    #61
  2. remat457

    remat457 Founding Member

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    I agree with you 100% ... I was always afraid of getting 3.55+ because everyone told me they pull so hard and ruin your gas mileage.

    I can't believe stock Mustangs come with anything less steep than 3.55...
    #62
  3. BAFMustangGT

    BAFMustangGT New Member

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    My friend with a 95 Cobra just got some 3.55s, ill let you guys know how he/I like them. I wish he woulda got the 3.73...
    #63
  4. drgn5.0

    drgn5.0 Founding Member

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    It's not a matter of being sensitive. What i'm talking about is tact, and a lack of respect. Yes, this is the internet, a place where people say and do stuff to others they wouldn't even think about doing in reality. I really don't care what 99.9% of people do or don't do when it comes to gearing and turbo's. I'm not them.
    #64
  5. mooktank

    mooktank New Member

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    hey howabout we talk about the gears dude. Stop being a schmuck.
    #65
  6. ratrapp

    ratrapp New Member

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    believe it or not a little lower gear than stock takes some strain off of the motor because the motor has exert extra force to get moving when it's fighting against 2.73 or a 3.08.prime example is i've been helping the owner of the next door bodyshop who just bought a decent 72 chevelle that was supposed to have 3.73 gears but no posi.i installed a powertrax unit in it and counted the gears and it had 2.73,he argued that the motor seemed to rev harder than 2.73s but after we drove the car and i let him drive a friend of mines 72 chevelle with 3.31 he was like oh i understand now.thats why most mustangs actually get better gas mileage with 3.55 or 3.73 gears.
    #66
  7. Michael Yount

    Michael Yount Advanced Member

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    I agree, with all things equal the gear will usually help around town mileage a bit. Highway mileage, however, usually is hurt - even though not by much if the gear's modest (3.55's or 3.73's) by more gear.
    #67
  8. mooktank

    mooktank New Member

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    I still cant decide if i should just put in the 3.55s i have or buy some 3.73s. help!!!
    #68
  9. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    as Michael posted in one of these rear gear threads, the difference will be almost negligable - id run what you have, esp if you are doing the install yourself (so labor costs are offset, should you decide to step up later).

    im very tame compared to you folks - ive always thought that 3.55's would be great. but im on the other side of the spectrum from you guys (i know a guy who ran 4.56's in his late model cobra). i think his top speed was 60 mph. LOL.

    Ratrapp, good point about the stock gears 'lugging' around. :)
    #69
  10. Michael Yount

    Michael Yount Advanced Member

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    They're so close in my mind that there's no question - put the one's in you already have.
    #70
  11. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    :OT: Michael, congrats on 5K posts!
    #71
  12. RydeOn

    RydeOn Licensed to Chill Founding Member

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    :cheers:
    #72
  13. 93-331-29psi

    93-331-29psi Member

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    You want to talk about bad gearing. Try doing 3.08s with a (.50) 6 speed! I think that 4.10s is in my near future of not 4.30s. Any advice???
    #73
  14. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    first off, Ryde On, you are not doing too shabby yourself (i'd have done the same had i seen your 6K-th post). :)

    93-PSI, it depends upon your motor and trans gearing. if you have 500hp, the final drive you have might not be bad. give more info so the smart people (not me) in here can toss some numbers at you. :)
    #74
  15. bryant99

    bryant99 Founding Member

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    3.73 with a t-5 and I like the combo
    #75
  16. MustangLX-5.0

    MustangLX-5.0 Founding Member

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    Having a '92 with stock 2.73's in a convertible with Auto. Trans....my car just lugs around.1st and 2nd gear seem to be ideally closer in ratios but then when it hits 3rd & 4th,the RPM change is more dramatic.You know your car is slow when you can't even powerbrake it unless the road is wet :rolleyes: .Was seriously considering gears and thought for awhile that 3.55's would be ideal.I heard....and this was only hearsay,that going anything higher than 3.55's (eg. 3.73's) on a car with an Auto. Trans. can mess up the computer.Something about the tranny not shifting properly or sometimes not shifting at all.I don't know :shrug: I just need something that'll give this car a good kick in the ass! Yet not tach out so high on the freeway as to ruin gas mileage or cause excess crank/rod bearing wear.

    How much of an RPM increase would one be looking at in the highest (Overdrive) gear which is 4th on this car,going from stock 2.73's to 3.73's?
    #76
  17. yellow5.0cobra

    yellow5.0cobra Founding Member

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    dude, just chill out.

    how old are you anyway?

    :rolleyes:
    #77
  18. mooktank

    mooktank New Member

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    im pretty sure RPM increases are directly proportional to gear changes. As in there are no squares or inverse squares involved. try doing some calcs. 4.10s are supposed to be good for an auto. It might mess with the computer if you dont compensate for your speedo being off.
    #78
  19. RydeOn

    RydeOn Licensed to Chill Founding Member

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    Yea Ive posted my share of useless bull**** around here. :D
    #79

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