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What gear?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Flyinhi86, Jun 9, 2001.

  1. Flyinhi86

    Flyinhi86 Registered Member

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    I have a 700R4 tranny with 3:73 gears, 350 motor and 35" tires. To save the tranny from burning out should I drive it in overdrive all the time. Should I be worried about possible tranny, motor problems with this setup.
     
  2. '73 K5

    '73 K5 1/2 ton status

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    Driving it in overdrive would probably hurt more than help...unless you are driving 75 or something. With only 3.73's and 35's, its going to be lugging around at a lower RPM anyway...add an overdrive to that and it gets way worse...the engine won't even be close to its proper powerband anymore. 4.56 gears would be alot more suited to 35's....even 4.88's would be fine since you have the overdrive.

    '73 K5
    Chevy good...Ford bad
     
  3. KENT

    KENT 1/2 ton status

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    What is the proper power band (RPM) for a 350 motor? Does FI make any difference?

    I'm running 33" with 3.42 gears in my 89 blazer (250/465/241). It doesn't seem to lug down noticably. I am upgrading to 3.73 with 35-36" tires and though that would be about right.

    Am I totaly off base?

    Kent

    1989 K5
     
  4. '73 K5

    '73 K5 1/2 ton status

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    There are websites that have gear calculators on them so you can type in your tire size and gear ratio and it will tell you what cruise RPM will be at 65 mph. Maybe someone else can list a link to one of those websites, because I can't remember any off the top of my head.
    I think most of the guys here would agree for a 50/50 payoff between offroad and highway driving that 4.11 gears are a great match for 33's. Thats what I have and I love it. 4.56 gears for 35's or 36's...and so on.

    '73 K5
    Chevy good...Ford bad
     
  5. fatdog

    fatdog Registered Member

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    Try this calculator link, http://www.randysringandpinion.com/RPMCalculator.html not sure about the actual accuracy, but maybe some of you can verify with your current set-ups.
    Rob

    '65 Turbo Corsa
    '69 Elcamino
    '71 Chev 4x4 Short Step
    '71 GMC 4x4 Long Fleet
    '72 Chev 4x4 K5
     
  6. thatK30guy

    thatK30guy 1 ton status Premium Member

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    What about what they say when driving around town, keep the tranny in Drive mode and when on the highway, keep it in the Overdrive mode?

    <font color=red>I m so we Todd did.
    I m sofa king we Todd did.</font color=red>
     
  7. gokartergo

    gokartergo 3/4 ton status Staff Member Moderator

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    Power band for a 350 is 1800 to 2800 rpm at 60 MPH.
    <A target="_blank" HREF=http://www.ring-pinion.com/>http://www.ring-pinion.com/</A> And go to calculator........Dan
     
  8. Triaged

    Triaged 1/2 ton status

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    To save the trany get a big cooler. 700r4's hate heat. There are also kits out there that will lock the converter up sooner (by speed insted of just in 4th gear) to keep it from making heat but you would need enough power to have it lock up sooner.

    '71 Blazer CST with alot of rust
     

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