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Gear ratios...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Emmettology 101, Sep 13, 2000.

  1. Emmettology 101

    Emmettology 101 3/4 ton status

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    I know this is one of those Beat to death topics, but a chart I just looked at sort of threw a shoe horn into the works.

    I am running 35's right now and may go to 38's on my nex tire purchase. Well I have to buy front gears now and thought that if I am going to change them in the future I might as well go with the ratio I need for the future.

    i was going ot go 4.56's, but then figured that would be to high for 38's.. Then i thought 4.88's, but then I looked at a chart on 4wheel parts webpage and 4.88's are in the "good Fuel " range. According to thier chart, 5.13, 5.29, 5.38 and 5.71 would be a better choice.

    I do a little street driving and dont want to be running 5K rpm at 60, but I want a really low, low range. A doubler is in my plans for the future, but that is a ways off.

    I am running a 350/TH350/NP208 combo and I just think that the gears in the 5's may be too low.

    I saw some has that they run 38's and 5.13's... What tranny are you running and what RPM are you running at 60?

    About 80 miles is the farthest I drive this thing on the street, but I dont want to use a full tank to go that far. Right now I am getting about 8.5 MPH with 35's and 4.10s...

    What is the general concensus on this?

    Below is a link to the chart I am looking at, but it is rather fuzzy and small.

    http://www.4wheelparts.com/product2.asp?imseqn=253&occlass=DANA&cat=DRI

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; http://emmett.coloradok5.com
     
  2. WakeBoard&4X4er

    WakeBoard&4X4er 1/2 ton status

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    I am running 3.42 on 33, I know this does not help you(sorry), but are you looking to get rid of your 4.10s? if so,how old are they, what would you want for then, would they fit in a STOCK 91K? Thanks

    BIG COX
     
  3. Emmettology 101

    Emmettology 101 3/4 ton status

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    My front 4.09's are scrap since the ring gear is missing some teeth and the pinion tried mating with the carrier. The rear 4.10's are Richmond and only have about 600 miles on them, but they are for a 12 bolt and i dont know if I am going to sell them or not.

    But I will let everyone know if I do.

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; http://emmett.coloradok5.com
     
  4. Executioner

    Executioner 1/2 ton status

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    Location:
    Temp. Ft. Walton Beach Fl. home=Tucson, Az.
    Since you don't have a low 1st gear, and don't have an overdrive, its just smiple math, pick the gears that
    give you the curuise rpm that you can handle at 60. or 80, or whatever your freeway speed will be .
    Throwing the doubler into the picture will help your crawl ratio, but still will not do anything for you freeway speed.
    If you really want the best of both worlds, low crwal ratio, and low rpm's at freeway speed, you are going to
    have to bite the bullet and get an overdrive.
    Good luck
     
  5. Emmettology 101

    Emmettology 101 3/4 ton status

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    Well the Doubler would help since I could run a higher rear end ratio and yet still have a good crawl ratio.

    Thanks!

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; http://emmett.coloradok5.com
     
  6. Blazer79

    Blazer79 1/2 ton status

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    Why don't you go to http://www.4lo.com? There's an online gear calculator that will help you determine the exact RPMs you'll be running with each gear.

    Tip: Input the real diameter of your tires in the calculator, since they are usually smaller than advertised. That way you won't get surprises.

    <font color=blue>//////
    http://blazer79.coloradok5.com
    </font color=blue>[​IMG]
     
  7. Emmettology 101

    Emmettology 101 3/4 ton status

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    I went to Randy's Ring and Pinion and used their calculator.
    Here is what I came up with:

    4.56
    35 - 2697
    36 - 2622
    38 - 2484

    4.88
    35 - 2886
    36 - 2806
    38 - 2658

    5.13
    35 - 3034
    36 - 2950
    38 - 2795

    These RPM's are for an Auto tranny without O/D.....

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; http://emmett.coloradok5.com
     

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