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72 Blazer axles

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by achuskies69, Mar 4, 2001.

  1. achuskies69

    achuskies69 1/2 ton status

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    <font color=green> I bought a Dana 44 and a GM 12 Bolt along with a NP 205 off of a 72 Blazer. Got all of it for $150 cause the guy had no use for em. They are in good condition but i was wondering if anybody could tell me what gear ratios were avaliable in 72? i am hoping they are 3.73's because im running 3.08's in 10 Bolts and wanting to go from 33's to 35's on my tire size.

    <font color=green> I love cowboy hats
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  2. Well I can't tell you what you have in your pumpkins but I can tell you that 3:73's were available in 72 because I have them in mine. When I bought my 72 it already had 33's on it. I had the truck for just under a month and the rear end blew, so that's how I know it had 3:73. I find that my truck is a little sluggish off the line with 3:73s and 33's but this could just be because the engine is so old and tired. I am hoping to rebuild my engine this year to help this situation.

    72Blazerod
     
  3. travis

    travis 1/2 ton status

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    I'd say most likely 3.73's. The backyard way to find out is put the rearend up on stands, have a bud hold one side still while you spin the other axel. If the yoke spins 3-3/4 turns....you have 3.73 gears.
     
  4. Blazer1970

    Blazer1970 1/2 ton status

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    In '72, standard gear ratio for 6 cyl. and 307 trucks was 3.73. Standard ratio for trucks with a 350 was 3.07. I believe 350 trucks could be ordered with 3.73, but you wont see too many that way.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
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  5. smp

    smp 1/2 ton status

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    I had 3.73s in mine and if you are putting them under a newer blazer you will have to move the rear spring perches.



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  6. achuskies69

    achuskies69 1/2 ton status

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    <font color=green> yeah i know about moving the spring perches on the axles, im gonna do all the work about going through the seals, check the gears, and fix the perches in my dad's shop, he has a welder so thats a plus. I have to call the guy sometime and find out what kiind of motor was orginially in the 72 so i know what gears they are,

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  7. Burt4x4

    Burt4x4 3/4 ton status

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    Hmmm, mine is a 350 and has 3.73 and none of the previous owners had anything to say they did a gear change so could be eather way???..........

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  8. travis

    travis 1/2 ton status

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    I guess spinning the axle and counting the revolutions is too much work? LOL. Don't go by what type of motor it had. Mine came with a 350 and 3.73's. I'd hate to see you go through all of the trouble moving the perches and everything just to find out it has the wrong gears.
     

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