1. moparmike98

    moparmike98 Well-Known Member

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    Looking at swapping my 3.23s with a guys 4.10s. Wondering if anyone runs 4.10s on a 27.5 tire on the street. Are the rpms ridiculous or are they just a lot of fun. Not looking for interstate riding. Also I have the 741 case is that an issue.
     
  2. AJ/FormS

    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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    If you didn't blow it up with 3.23s then the 4.10s will be cake for the case.

    As to rpms, the 27.5s will call for 3007 rpm at 60 mph with a M/T.That'd be almost like driving in third with 3.23s, which calculates to 3316rpm.
    That's too much for me....... but I'm getting on in years,lol
    I gotta tell you though, 2.66 x 4.1 = 10.91. That's a generous starter gear for a motor that puts out 440ftlbs. As a streeter and on a daily basis, you will be spending an awful lot of time shifting, especially the 1-2. I hated it with 4.30s.
    Consider also what the rpm will be at your typical city driving speed. For instance; at 30 mph and with 26.5 inch tires, your current rpms with 3.23s are 2360 in 2nd , and1720 in third. With 4.10s it will be 2995 in 2nd, and 2184 in 3rd. Somewhat obviously, you won't be cruising around at 2995, so, Notice that you have traded a nice 2360 in 2nd for a lesser 2184 in 3rd. And downshifting from 3rd to 2nd is often a crapshoot with an old shifter.A better solution for this instance would be 3.55s which would put you at 2594.
    The engine doesn't care what the diff ratio is once the car is cruising. It only cares what the total reduction ratio is. IE, you could have a 4.10 diff and a 1.92- 2nd gear, or a 1.92 diff with a 4.10- 2nd gear, the reduction is the same 7.87. There are only two places the 4.10s can help you; getting of the line and trapping at an optimum mph at the track. With 440ftlbs available, I can't see getting off the line being a problem.And trapping well is not a concern. So..... If I was you, I'd gear it to be at an optimum rpm at the speed you are spending the most amount of time, where you want a good amount of torque multiplication.
    For me, that was 3.55s and 2nd gear. with 295s on the back, 30 mph in 2nd is 2582. Like you I have a generous amount of torque there, being able to light them up, at will.
    Your results may vary.
     
  3. EL5DEMON340

    EL5DEMON340 Well-Known Member

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    If you don't go to for long drives on the expressway they will be fun. They should help you launch from stop light to stop light!!!
     
  4. clinteg

    clinteg Well-Known Member

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    They're a lot of fun if you're not highway driving all the time. Mine does 3000-3100 rpm @ 60 mph.
     
  5. 1967 'cuda

    1967 'cuda Dropped on Head as a Baby

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    As stated above, the 4.10s are great in town. Personally I wish I'd have gone with 3.55s instead. I'll probably change mine out some day unless I install an overdrive. The constant 3000+ RPM going down the highway makes me concerned about engine wear.
     
  6. inertia

    inertia Well-Known Member

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    Just about the constant hi RPM thing..

    Keep in mind many of the automotive marine conversions, are run continuously for hours and hours on end, uphill, with a red line of about 4k,, and std cruising rpm of between 2400 and 3500 rpm,, hour after hour, for hundreds of hours.. uphill..

    Some boats run wide open (governed) from dock to dock,, all their lives..

    jmo

    Cruising at 3K... The discomfort is solely yours,, not the engines..
     
  7. 1967 'cuda

    1967 'cuda Dropped on Head as a Baby

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    Maybe you're right inertia. I guess I'm assuming the rate of wear would go up exponentially with the RPM. Maybe I'm just overly concerned because I've got more $$ in my motors now than I did when I was much younger and I'm more afraid of breaking them. Maybe it's just because I'm becoming an old coot. LOL.
     
  8. inertia

    inertia Well-Known Member

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    LOL... I'm an old coot too... but my 340 @ 3k in any gear is sweet music to my ears...

    It's the Overdrives we have become accustomed to,, running a motor a 3k was a norm,, and 4:10's were the go-to "3/4 race" gear..to go with the "3/4 race" cam.. lol

    I ran 5:12's between races,,, 60mph on short street tires was about 3800 rpm..
    the track being about 20 hiway miles away.. lol
     
  9. 1967 'cuda

    1967 'cuda Dropped on Head as a Baby

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    It's probably those dang Purple Hornies I'm running that keeps me worrying. I suppose if I quieted it down a bit I wouldn't be as aware of the RPM.
     
  10. diymirage

    diymirage HP@idle > hondaHP@redline

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    consider this, the motor is at temp, there is a steady airflow cooling the radiator and ample and steady oil pressure
     
  11. 1967 'cuda

    1967 'cuda Dropped on Head as a Baby

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    True. At 3000 RPM I guess there's plenty of motor left. It's not as if I'm running it anywhere close to it's limits.
     
  12. DartVadar

    DartVadar Well-Known Member

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    I just put them into my dart and absolutely love them! like stated its a bit over 3000 on the highway, but I built my motor to have fun with and that why I put those gears in. Off the line takeoff burns the tires into second and third so better tires may be a good idea.
     
  13. Woods74

    Woods74 Quick Senior

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    • Like Like x 1
    • 1967 'cuda

      1967 'cuda Dropped on Head as a Baby

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    • 4geardemon

      4geardemon Well-Known Member

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      I have 4.10s in my 4 speed demon. Love them!! had intentions of getting a higher gear for the highway and swapping just for the track but decided to keep what I have for the stop light to stop light fun. Eventually will get some 3.23s for the future road trips that it will do but that won't be for awhile.
       
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