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Thread: mud racing gears

  1. #1
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    mud racing gears

    ok guy help me out im a bog and fast track racer the truck is a heavy 4600 pounds it has a 468 about 650hp im running 4.10 in low side of a np208 and pulling high gear in a th350 my crawl is 10.7.1 and my mph at 6500 is 69.6 im thanking about go to high side of my 208 and useing 7.17 gears it would make my crawl10.91 in 2nd gear and my mph 68.3 the proublem i have now i cant get to high gear fast enough

  2. #2
    Senior Member RACING JUNKIE TheRabbit's Avatar
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    You didn't say what size tires you run. I couldn't figure it out because 39's with 4.10 @ 6,500 = 66mph and 44's @ 6,500 = 75mph ( that's using 39"'s and 44"'s for the math. Tires are almost always 1.5" to 2"'s shorter than what they say they are, but don't get hung up on tire speed)

    Two problems going with a gear lower than a 6.20.
    1. You can't get a match for the front gear. Even with 38's on the front you'd need a 6.50 front gear to match.
    2nd The pinion is getting way to small to handle the power / abuse

    Also if you're hitting high gear with only 650hp with a 4600lb truck you aren't hooking up very well even if it's muddy as heck.

    High side is the way to go, but need a little more info about your truck and tracks you run.
    Just as a base idea I use to run (with a gutted 208 case) a 6.20 rear with 44's and a 5.13 front with 38's, but was over 1,180hp in a 3600lb truck. It ran a best time of high 3.2's in 200' on DOT's and constantly ran low 3.0's to high 2.9's on cuts.

  3. #3
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    sorry i run a non cut tire 38.5 11.5 15 i run deep bog pits and real dry dirt drag side by side. what I'm trying to do is get to my final faster i should be OK with the smaller pinon I'm using a stock 10 bolt now with no problem i just got a 9in front with 60 outers that's going up front any help at all on what gear to try would be great thanks for all your help

  4. #4
    Senior Member RACING JUNKIE TheRabbit's Avatar
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    I'll look more into it tomorrow when I have some time to play with the #'s, but you do know every time you shift your loosing time?

  5. #5
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    i under stand that. thats why i want to run high side and just shift to 2nd shifting to drive is killing me now what ever you come up with would be great thank you so much

  6. #6
    Senior Member RACING JUNKIE TheRabbit's Avatar
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    A 7.17 gear would only give you 61mph tire speed at 6500 rpms.
    A 6.50 rear and a 6.20 front ( if you run 38's on the front) would probably work better. You would probably run better by just using 2nd gear only and not shifting at all.


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