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? on rearend

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blazerblk, Mar 29, 2001.

  1. Blazerblk

    Blazerblk Registered Member

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    Right now my K5 has a 12 bolt 3.42 rear. Would I feel much of a difference if I swapped in the 10 bolt 3.73 rear? I have 33 12.50 15 tires, 700R4, 350TBI. Or would it be better to just swap out the gears to the 12 bolt? I don't go crazy off-road. No mudden or climing over large objects. Also, what gear would be better? Thanks for any suggestions.
     
  2. Wheels

    Wheels 1/2 ton status

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    Between the two axles, the 12-bolt has a slight edge over the 10-bolt. My vote would be to keep the 12-bolt and swap the gears.
     
  3. Emmettology 101

    Emmettology 101 3/4 ton status

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    If you swap an axle into the rear with a different ratio, you will need to do so on the front also! Especially if you use 4wd on hard pavenment..

    I would stick with the 12 bolt.... And then swap gears into it..

    I dont think you will notice much of a difference going from 3.42 to 3.73..

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

    chvyhs 1/2 ton status

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    I have '77 K5 with 35" tires and a 12 Bolt with 3:73 gears. I used to have 33" tires and when I switched to 35's I could tell the difference. If you can get the 10 Bolt for free or real cheap I would go for It. just be advised that a 10 Bolt is supposed to be weaker than the 12 Bolt. The gear change would be felt in aceleration, towing, and climbing. Your top end speed would also be reduced. I'm planning on going with a 4:56 gear when I get a 14 Bolt. Go to this web site and check out their gear calculator.

    http:chvyhs.coloradok5.com
     
  5. Blazer1970

    Blazer1970 1/2 ton status

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    With the OD trans, if you are going to swap gears, go with 4.10s or 4.56s, not 3.73s.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     
  6. CaptCrunch

    CaptCrunch 1/2 ton status

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    3.73's would give you a little boost and still keep everything good on the freeway... 4.10's would help downlow, but affect freeway cruising mpg. It will be hard to find a 12B combo w/ 4.10's though... I just got lucky as heck and stumbled on one, but I somehow have this feeling I'll be swapping them out for 3/4 4.56's LOL... but we'll see. I'll be running 35's btw.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     

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