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Rpm On The Highway

Discussion in 'Intermediate CJ-5/6/7/8' started by Iandavidh, Feb 3, 2019.

  1. Feb 3, 2019
    Iandavidh

    Iandavidh Member

    California
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    What would be a comfortable rpm on the highway for long periods of time? Im running a 258 with a t18 and 4.10 axle gears on 31s. I know the tire size and gear ratio isnt optimal for the highway but its what i’ve got. I am pulling around 2600-2700rpm at 60 mph.
     
  2. Feb 3, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    What year? You're fine. The factory 4.27 ratio is fine even with the shorter factory tires. How fast do you want to go?
     
  3. Feb 3, 2019
    Iandavidh

    Iandavidh Member

    California
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    Its a 1973. I was wanting to do around 65-70.
     
  4. Feb 3, 2019
    mike starck

    mike starck Member

    salem,oregon
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    Those numbers are a little high to be called comfortable.200-300 rpm drop would do wonders. Problem is how to get there. Gears or tires and loose off-road performance. Or live with it and get a second vehicle.
     
  5. Feb 3, 2019
    mike starck

    mike starck Member

    salem,oregon
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    3.73's
     
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  6. Feb 3, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    70 is about 3100. Does that worry you? It's fine for the engine if in good condition. I would take measures to dampen the engine noise and drive it.
     
  7. Feb 3, 2019
    Iandavidh

    Iandavidh Member

    California
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    The engine is in good working order. I’ll try having it up at 70mph at see how I feel about it.

    Eventually I will go up to 33s which would definitely help.
     
    Last edited: Feb 3, 2019
  8. Feb 4, 2019
    johneyboy03

    johneyboy03 The green beast

    Quebec, Canada
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    3.73" in axle, 36" tire runing around 2200 at 60 mph
     
  9. Feb 4, 2019
    sterlclan

    sterlclan Member 2022 Sponsor

    exploring the...
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    373 with a 32 about 2500 at highway speed.
     
  10. Feb 4, 2019
    mike starck

    mike starck Member

    salem,oregon
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    With the numbers you gave I think your on the right track . 33" with 4.10's might be the sweet spot for you.
     
  11. Feb 4, 2019
    Iandavidh

    Iandavidh Member

    California
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    Thats what i was thinking.
     
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  12. Feb 4, 2019
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    I ran my Tux up a bit higher than the "9" on the speedo several or more times in my younger day. 235/75-15 tires with 4.27 axles, and a Buick 215 that liked high rpm. I never had a tach, but I'm guessing I was approaching 5K. My friend's Ford F150 4x4 couldn't keep up.
    I ran that combination a lot on the interstate at an indicated 70mph, and it was comfortable for an hour or two, no problem!
    I really like the 4.27 gears for all-around use. I never had a good overdrive back then.
     
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  13. Feb 18, 2019
    Iandavidh

    Iandavidh Member

    California
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    Had it up to 65 the engine was at around 2800 handled it really well it just was very loud! Have not had it on the freeway yet because its been very wet down in socal and I do not want to go the fastest i’ve gone in it on a wet freeway.
     
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