Gear ratio ?

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    Author Topic: Gear ratio ?  (Read 2995 times)

    Offline whitesatinmopar

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    Gear ratio ?
    « on: February 17, 2004 - 07:14:58 PM »
    As some of you know I'm building a Roadrunner clone, and one of the areas of question is the rearend that came in the car, which another guy(previous owner) had installed. He said he wasn't sure of the gear ratio. Well I know enough to count wheel to gearbox reveloutions and here is what I came up with. The yoke turned 4 and aprox. 1/4 to 1/3 times, that with the fact that it is a 12 bolt pattern I think I probably have a 4.30 rearend, and it is a suregrip. Two questions: What could this came out of, and do you think it to be too low for street/road use? This will be powered by a built 440+6 and a built 727, other than gas and tires is there any reason to consider changing it? Thanks
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    Offline GhettoPop

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    Re:Gear ratio ?
    « Reply #1 on: February 17, 2004 - 07:34:12 PM »
    a lot of highway cruising w/ 4.30s will put more wear and tear on your engine, and other things, since u will always be driving at a higher rpm.  if u drive a lot of highway, maybe go w/ something in the 3's, but if u love traffic light racing, dont touch them! i got 4.30s in my chally but since highway cruising is not really an option in NYC, i love em! peace
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    Offline Chryco Psycho

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    Re:Gear ratio ?
    « Reply #2 on: February 17, 2004 - 07:38:20 PM »
    as long as both tires were turning equally this method is accurate , for a street strip car I would change the gearing even with a 30" tire you will be 3500 rpm + on the highway  
    « Last Edit: February 26, 2004 - 10:24:55 PM by Chryco Psycho »
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    Offline whitesatinmopar

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    Re:Gear ratio ?
    « Reply #3 on: February 17, 2004 - 07:52:18 PM »
    I have no plans for any prolonged road use, perhaps on average 30 miles maybe, but I see your point, so "down the road" what ratio would you suggest? This year if I get it back together this set up will have to do ($$$$$ getting less and lesser), the 3.55's be a good choice? Thanks guys.
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    1969 Polara 500 vert.
    1970 Charger 500
    1971 Dart Swinger
    1972 R/R 440+6 (wanabe)
    1973 Challenger

    Offline Chryco Psycho

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    Re:Gear ratio ?
    « Reply #4 on: February 18, 2004 - 01:30:06 AM »
    3.55 is Fun
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    Offline Carlwalski

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    Re:Gear ratio ?
    « Reply #5 on: February 18, 2004 - 01:52:18 AM »
    Agree  :D 3:55's give you the best of both worlds, good pick up and good highway rpms  :)
    « Last Edit: February 18, 2004 - 01:52:57 AM by NZ 440RT »
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    Offline oldvamoparfan

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    Re:Gear ratio ?
    « Reply #6 on: February 18, 2004 - 10:53:42 PM »
    Hello Folks,  Remember the OD trans we have been talking about?  If you want to keep the low gears for acceleration, then look for an OD trans hookup.  If you can come up w/ one, you would then have a 2.96 overall ratio in Od, which is a great highway gear.  It would take a bit of calculating, but it would take a heck of a tall tire to even come close to that.  Ovmf  
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    Offline whitesatinmopar

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    Re:Gear ratio ?
    « Reply #7 on: February 19, 2004 - 09:11:44 AM »
    Good point ovmf but I already have the 727 built to the hilt for some possible rugged use, not bullet proof but very durrable, it sure won't be a marshmellow,lol.
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    Offline oldvamoparfan

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    Re:Gear ratio ?
    « Reply #8 on: February 20, 2004 - 09:31:01 PM »
    W/O OD, a 3.23 is probably the best all around gear unless you plan to do a lot of dragging off from a start.  A 3.55 would be a slight concession toward the low end accel while not being too bad on the road.  Anything lower means a lot of rpm at road speed & terrible operating cost in addition to higher engine wear.  If roadability is more important than all out accel, then a 2.94 or 2.71 would give great (& quiet) road performance & improved economy.  Only you know how you intend to use the car.  Another item often overlooked is the speedometer gear.  Anytime you change rear end gears, transmission, or tire size, you need to check the speedo gear to see if it agrees w/ your present set up.  Year one books have a chart w/ most of the popular combos & the appropriate speedo gear.  If new ones are needed, you local Chrysler dealer can supply at a reasonable cost.  This can save you money in speeding tickets, as well as giving accurate mileage for keeping your car serviced.  Ovmf
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    Offline whitesatinmopar

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    Re:Gear ratio ?
    « Reply #9 on: February 21, 2004 - 09:26:28 AM »
    Thanks ovamf, this car is bassically a street machine, no prolonged highway use, just something to, well have fun in, I may (probably) will take it to the strip a couple times before removing the 4.30 gears just to see what kind of time slip I call get,lol. But then I will probably be changing to the 3.55 rear, it is kind of in between, gives you "reasonable" road use and still provides a litle extra kick when you may want it. My Charger 4 spped has the 3.23 gears and I agree it is a real good ratio for over the road.
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    1969 Polara 500 vert.
    1970 Charger 500
    1971 Dart Swinger
    1972 R/R 440+6 (wanabe)
    1973 Challenger

    Offline DodgeFreak

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    Re:Gear ratio ?
    « Reply #10 on: February 24, 2004 - 10:34:36 PM »
    3.93 gears would work too give more kick in the butt but still be fairly decent on road....my dads truck my truck with 318 518 od off it engine spins 3 grand or close to it thats with 3.55 gears dads truck had 215-70-r15s mine had 235s-75-r15 or it was 235 70s but about the same soo that will give you some sort of an idea about where 3.55s will put you.
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    Offline oldvamoparfan

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    Re:Gear ratio ?
    « Reply #11 on: February 26, 2004 - 07:12:30 PM »
    Even the 4.10 wont be too low w/ OD, as that will yield a 2.87 overall ratio, which would be a very good road gear, while still having lots of low end get up.   Ovmf
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