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Gearing/Stall speed question

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  • Gearing/Stall speed question

    This winter, the 408c will be getting put into my truck. The 9" has 4.86 gears in it but I'm guessing that those gears might be a little too low for the added torque of the 408 vs the 351. I'm guessing my stall speed will change a little too with the added torque, but unsure of how much. I have a set of very lightly used 3.89's. But, here is my problem. I'm running a Gear Vendors overdrive so the 4.86's appear to be 3.79's. I still run about 3200-3300 rpms @ 60. If I'd put the 3.89's in, they would appear to be 3.03's. My current stall speed is about 4000-4100 flash. I have two big coolers on the outside of my radiator and the fluid doesn't go through the radiator, so the fluid should stay cool. But, will it hurt the converter to be "slipping" that much when cruising?

    Also, do you guys think I should keep the 4.86s or will the 3.89s be better with the added torque? This is in a 3800# truck.
    1994 Lightning "Pro Street"
    *Old Combo* 408c CHI 3V 225cc Heads, 3v Intake, Dave Storlien solid roller, Rollerized c6, UCC 6,000 rpm converter, Merkl Racing 'brake, AJE k-member front suspension, and Outlaw 4 link with Koni da coilovers.
    715hp and 604 ft lbs @ the flywheel on pump gas.
    [email protected] 1/8th
    [email protected] 1/4
    1994 Lightning 408c 3v

  • #2
    I'd leave it alone until you try it with the new engine. I don't think the 3.89 is the right gear for you with the GV unit.
    Ben
    '93 & '97 champion of Central Indiana Dirt Racing Asc.
    C.I.D.R.A.
    __________________________________
    '79 Fairmont 408C/C4 10.50 @ 127
    '70 Mach I 351C 4V toploader
    '07 Mustang GT

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    • #3
      Thanks Ben, I was kinda guessing that the 3.89's would be a little too high when paired up with the GV. Guess I'll just have to wait til spring and try it out and see what its like.
      1994 Lightning "Pro Street"
      *Old Combo* 408c CHI 3V 225cc Heads, 3v Intake, Dave Storlien solid roller, Rollerized c6, UCC 6,000 rpm converter, Merkl Racing 'brake, AJE k-member front suspension, and Outlaw 4 link with Koni da coilovers.
      715hp and 604 ft lbs @ the flywheel on pump gas.
      [email protected] 1/8th
      [email protected] 1/4
      1994 Lightning 408c 3v

      Comment

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