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'nother run of the mill ratio question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blazer_Boy, Jan 31, 2001.

  1. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    \'nother run of the mill ratio question

    Here's another question about what ratio to use. I know about the charts but I like hearing about people who've actually done it and how they've liked it (thank god for this post and everyone on it [​IMG], just thought I'd through that in 'cause I mean it and it somes everyone is a little touchy lately, including me). Anyways, time for details

    '82 Silverado
    350 crate /w quadrajet
    NP208C transfercase
    TH700R4
    Michelin 31x10.50x15 AT tires

    Whats the ratio for me?

    The charts say go 4.11 but I think thats a little steep. Then there's 3.73's but maybe thats not steep enough. The truck gets driven around town alot and on highways. I also do a little fishing, you know..gravel roads, mudholes, all that fun. I might do some hill climbing now and then out hunting. Basically it won't see the kinda heavy action like Rene (hi buddy) or Steve . I just wanna hunt down a 12 bolt out of old chevy and drop it in and get them RPM's back to where it should be cause they're way to low.

    June 2001 - The Texas Sawz All masacre begins. Be afraid rust, be very afraid. [​IMG]
     
  2. Wheels

    Wheels 1/2 ton status

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    Re: \'nother run of the mill ratio question

    On mine with 33's, the recommended ratio was 3.73 to 4.56 (350/350/203). I went with 4.10, plan on a 700R4 as the next upgrade. Changing to the 700R4 and in OD, the RPM's at 70 mph will drop from 3000 (currently with the TH350) to 2100. Love the TH350, but I too have some long trips to make to get to my favorite spots and need the OD or drag the bank loan officer with me. With 31" tires I would look at 3.73 as the mid range (optimum) and 4.10 as the upper range. If later on you plan on going to 33's, go with the 4.10's now. I have a Z71 with 3.73 and 265/75R/15 tires (31.6" tall) and at 70 it runs at 2000 rpm in OD. Randy's Ring and Pinion has a rpm calulator that is pretty close to what you'll be running. It also has the recommended rpm range for different types motors, auto's, OD's and manual tranny's. (ring-pinion.com) Check it out.
     
  3. '73 K5

    '73 K5 1/2 ton status

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    Re: \'nother run of the mill ratio question

    You've got an overdrive. Go with the 4.11's.

    '73 K5
    Chevy good...Ford bad
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: \'nother run of the mill ratio question

    I agree, go with the 4.11's, you have the overdrive and if you are anything like the rest of us you'll probably go with bigger rubber in the future. It''ll have some good snap with the 31's and still do well if and when you go to 33's.

    Rene

    [​IMG]
     
  5. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: \'nother run of the mill ratio question

    I'll probably keep the 31's on the '82 because they're real nice in the city and the snow. My dads get 33 Goodrich M/T and they're pretty scary on hard snow. If I get the money I might strip the '81 down to frame and build it on up. I hope luck is on my side this weekend because thats how I'm getting my axles. My uncle and I are going to pick up a junk '77 chevy truck to part out this weekend and I can have the axles. I just hope its packing a 4.11. If it has 3.73s I may have to learn to like 'em unless I get lucky and find another truck to part out.

    June 2001 - The Texas Sawz All masacre begins. Be afraid rust, be very afraid. [​IMG]
     

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