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Was looking at different gearing on a calc...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Paxx, Feb 18, 2004.

  1. Paxx

    Paxx 1/2 ton status

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    I plan on running 39.5" tires.

    Ok it says that if I run 4.56's with my sm465 and a 39" tire I will be at 2554rpm at 65mph.

    If I run 5.13's w/39" tires I will be at 2873rpm at 65mph.
    At 75mph I will only be running 3315rpm.

    This seems a little off to me. I had thought that with 5.13's I wouldn't be able to hit the highways but 2900rpm doesn't seem all that bad. /forums/images/graemlins/dunno.gif I dunno does this seem right to you guys? I drive 99% of the time around town and off-road, the only time I would ever hit the highways would be when I go to BB04, BB05, BB06,... and maybe the odd trip to wheel on the coast or something.

    If it is then I would much rather go with the 5.13's /forums/images/graemlins/thumb.gif My final crawl ratio would be 65.76 which would be great for the trails around here.

    It should also help me develop wheel spin a little quicker too right?
     
  2. kennyw

    kennyw N9PHW Premium Member

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    I cruise at 2500-3000 RPM on the highway (55-70 mph) with 4.10 gears and 33" tires. This with a 4 spd so no overdrive. I was getting 15 mpg too before I switched from a highway tread to a mud tread...

    I think the 5.13's would be great and if you really wanted to drop that RPM on the highway all you would need to do is add an OD tranny or aftermarket OD.
     
  3. Derf00

    Derf00 1/2 ton status

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  4. Smitty

    Smitty 1/2 ton status

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    That calculator is great!!! Thanks for the link!
     
  5. Paxx

    Paxx 1/2 ton status

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    yep thats the one I'm using /forums/images/graemlins/thumb.gif I just really thought that my revs would be much higher at highway speeds with the 5.13's. I'm pretty stoked to find out that they aren't though because the only thing keeping me from them was highway drivability. /forums/images/graemlins/peace.gif
     
  6. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Max,

    Try PMing Zakk.....he's running that combo (39.5s and 5.13s) and can probably tell you what it's like on the highway, and also about the "get up and go" around town. He runs a mild 350 so it should be a pretty accurate evaluation.

    My guess would be 5.13s. 39.5 is a pretty good sized tire and the extra axle gear can help to get those things in motion from a dead stop. Also, I think you already own an overdrive tranny (700R4 right?) so you don't want to run the risk of being under-geared for the highway (39.5 and 4.56 probably won't be enough RPMs to stay in O.D.)

    More food for thought..... /forums/images/graemlins/thinking.gif








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  7. Paxx

    Paxx 1/2 ton status

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    No, I'm actually using a 465/205 combo. I'll pm Zakk though and talk with him about it.

    lol I can already picture this conversation.
    I think he has a shrine to 5.13 gearsets at his place that he worships every night before he goes to bed. /forums/images/graemlins/bow.gif /forums/images/graemlins/histerical.gif
     

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