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right gears...

Discussion in 'OffRoad Design' started by jekbrown, Aug 28, 2001.

  1. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

    May 19, 2001
    Likes Received:
    Vancouver, WA, USA
    Hey gang, I am putting together an idea for how I want my truck to be in its "final" configuration. I'll have a 350, mated to a 700r4 (from Jet Perf), NP205, 4.56 gears, and 35x12.50s which will, someday (after a 1 ton conversion!), be upgraded to 37s or 39.5s. Once I have a fixed yoke...I'll be using some beefy high angle drive shafts (no more bad vibes!!) My 85 jimmy will be used for everything from hot dates and sand, to mudding, trails, and rock crawling...so versatility is a good thing. Anyone see any inherant flaws/weaknesses with that kind of engine/trans/x-case/gears combo? Any suggestions? I will prolly be ready for the new slush box and x-case within a few months...so I need to get a plan of what the heck I am gonna do. ;) Any thoughts would be greatly appreciated!

  2. Stephen

    Stephen 1/2 ton status Moderator Vendor

    Sep 15, 2000
    Likes Received:
    Carbondale Colorado
    That sounds like a decent plan so far. 4.56's or 4.88's would be wise, and you may want to consider carefully before you put any money into a 1/2T rear axle. I'd say start now with a 14FF, or some other beefy axle, so you go right to 8 lug before you get wheels and tires. That way you're ready for the D60 when the time (cash) comes.
    If you're looking to go to 37" and up tires, you should look to the 4.88 axle gears, or even 5.13's. Bigger tires and more lift create a lot of drag at highway speed and you'll need some RPM's to hold it at higher speed in overdrive.
    I'd plan on a CV jointed rear driveshaft right off the bat, I ran that same combo for a couple of years and never got the vibration out of it till I did a CV shaft. I ran 35-37" tires with the 4.56's and 4th gear was never very useful. Part of that is altitude and the resulting power loss, and part of it is having the motor cammed a bit high for 2000rpm torque, but regardless, looking back, I'd do 4.88's or 5.13's and a cv jointed driveshaft.

    Crawl ratio is OK with your dream drivetrain, I thought it was doing pretty good with the same setup till I put the Doubler in then I wondered how I got by without it. So you should be fine for a while with what you spec'd out.

    Making the world better, one truck at a time.
    <a target="_blank" href=http://www.offroaddesign.com>www.offroaddesign.com</a>
  3. 84_Chevy_K10

    84_Chevy_K10 Banned

    May 30, 2001
    Likes Received:
    IL, USA
    4.56s and an overdrive tranny will kill it in a hurry. Minimum is 4.88s. I'd go lower.

    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles

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