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Help w/gears

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 88K5Jimmy, Apr 3, 2001.

  1. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    I have a stock fuel injected 88, 350/700R4, 208, 31x10.5x15, 3.08. My question is what would my gas mileage be if I went to 3.73 w/my 31's? I plan on 33's in the future but thats a while. I mainly want better gas mileage. Does anybody have the same setup and what kind of mileage do you get?
    Thanks
     
  2. Emmettology 101

    Emmettology 101 3/4 ton status

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    GOing to 3.73's may help your around town mileage a little, but on the highway it is going to hurt you with those 31's. Althoguh with OD, it will help.... If you are planning to go with 33's, I would get the 3.73's and live with the mileage....

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

    " Ah.. Hong Kong, home of shiny green suit!"
     
  3. CaptCrunch

    CaptCrunch 1/2 ton status

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    You'll probably be about the same depending on how much freeway miles you do. 3.08's are just CRAP! WTF was GM thinking... 3.73's and 33's will be a great combo so I hear... also 4.10's would be an option depending on how much you wheel and what kind of freeway rpm you want... I have found the TBI's like about 2200 or so for decent power, ability to downshift, and milage. All of this is IMO.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  4. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    Thanks for the help. Anybody have any other good info??
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    I jsut did some "testing" with some gear calcs on my site, and it looks like going to 33" tires, with a 3.73, will equate to 3.50 compared to 3.73 with the 31" tires...it's going to hurt you on the freeway. Consider 3.42's or so I would guess. Complete axles readily available from Suburbans, which had stock ratios of 3.42's during the 80's. Paid $200 for the last pair that are in my truck now.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  6. 90K5

    90K5 1/2 ton status

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    Don't even bother with 3.42's. I have them with 33"s and they are not good. My truck has a few mods that help brink the power up, but I'm still going to 4.10's. Please don't go to 3.42's...actually...if you decide to though...you want a 3.42 rear end? lol Seriously, get 3.73's thats what these trucks should have had anyway, I don't know what GM was thinking...3.42's and a tow package?

    90K5

    See my truck at <A target="_blank" HREF=http://albums.photopoint.com/j/Albumindex?u=1329584&a=9886502>http://albums.photopoint.com/j/Albumindex?u=1329584&a=9886502</A>
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    I may be having a different experience due to my manual tranny, but the 3.42's in my truck, with 33's, has no problem moving that truck out smartly. Its no drag race winner, but it's also a mid 70's motor that isn't built up. I've just got true duals with manifolds on it. I guess with OD, 3.73's and big tires would be about optimal...with no OD, the 3.42's keep my RPM's in a respectable range.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     

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