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Old 73 K10 had 3.73 / New 87 K5 has 3.08 ????

Discussion in 'The Garage' started by stano, Feb 11, 2005.

  1. stano

    stano 1/2 ton status

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    I used to have a 1973 K10 short box with 3.73 gears and posi in the rear and went all over the mountains of Colorado and Wyoming. Really did not have any real problems. Crossed steams (foot and a half), two tracks, hill climb, snow, Loved that truck. but no rock crawling.

    Now we just bought a 1987 K5 (first Blazer) 350, 700R4, and 3.08's with posi in the rear. I was afraid of the 3.08 gear because I did not want to give up any of the performance of the old 73 with 3.73.

    Went to this site http://www.angelfire.com/fl/procrastination/rear.html and calculated it out as; 750 to 1500 RPM's is what I mostly use to get over hard parts.

    750 RPM -- 3.73 gear -- 2.52 TH350 first gear -- 31" tire == 7.358 MPH
    750 RPM -- 3.08 gear -- 3.06 TH700R4 first gear -- 31" tire == 7.338 MPH

    So it looks like a WASH for cruising moutain trails.

    Any body have any info on this.
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    As far as offroading I don't think the 3.08's will effect much since you have a 208 with a fairly low low gear range. It's noticeably lower than the case in your K10, infact, I bet the blazer will crawl better since the 208 should make a bigger difference than 3.73's vs. 3.08's

    Like I said in your other post, a set of 3.73-4.10's would really be nice for cruising through the Colorado Rockies.
     
  3. stano

    stano 1/2 ton status

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    I just assumed that the 87 208 and the 73 203 was the same ratio. Now I checked and see that the 208 is 2.61 and the 203 is 2.01 ratio.


    thanks rjf guitar
     
  4. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    If you keep 33's or under , its kinda ok . I wheeled on 31's , 32's and now 33's with 3.08's . Low rpm with the converter and 208 is pretty good . I have 3.73's now for cheap ( 200 bucks for 2 axles ) , but if its all you got for now it will work :k5: :k5:
     
  5. stano

    stano 1/2 ton status

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    thanks for the info


    87 K5
    stano
     

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