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i need gearing help

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by greatwhite, Jun 2, 2001.

  1. greatwhite

    greatwhite Registered Member

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    Location:
    san diego, california
    Im droping a new 330HP 350ci with a 700r4 trans by JET into my 72 blazer and have been getting mixed views of what gear ratio to put in. two people including JET said to go with 4.56 gears due to the overdrive, but other say that that is to much torque. OH, i have 33 inch tires. ok, back to the gears, another say go with 4.11. then i noticed that some one here uses that set up with a 375HP 350cid and is using 3.75. how does that gear or any other users with a similar set up perform?
     
  2. gokartergo

    gokartergo 3/4 ton status Staff Member Moderator

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    You could go here and figure out RPM'S<A target="_blank" HREF=http://www.ring-pinion.com/>http://www.ring-pinion.com/</A>. I just have a stock crate 350. I went with the 4.56. I do have the 700r4 also. I love it. I probably can't do 100 mph anymore. But I really don't want to either. I also have 33's. I am turning 2100 rpm's at 65. I can't check my gas milage because my speedo is so far off now. When I think I am going 65 it is pegged over 85....Dan
     
  3. greatwhite

    greatwhite Registered Member

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    thanks gokart. that web site helped a lot. im kinda with ya on the 100mph deal, but i still want some good highend. so maybe 4.27 will make me happy. that should give me 1826rpm at 60mph
     
  4. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color=blue>One thing to remember, these trucks are very heavy dont cut through the air at high speeds like cars do. For a car, 1826 rpm would be fine, but thats not enough power to push a truck. With 33s and the 700R4, you would be better off with 4.56s. Going to numericaly lower gears wont give you any more mileage. If anything, it'll take away mileage since the motor wont be in its powerband and will have to work harder to move the truck (which means you push the pedal harder and use more gas). If you put the 4.56s in, you will be very happy with them.</font color=blue>

    [image]http://bbs.off-road.com/wwwthreads_uploads/53-288682-mudpit3.jpg[/image]
     
  5. gokartergo

    gokartergo 3/4 ton status Staff Member Moderator

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    I agree. I know my mpg improved. I just don't now by how much. Plus I am not mashing the skinny pedal as much around town. But I went from 3.08 to 4.56. I haven't even broke them in completly yet so I am taking it easy. I thought at first that I might be going to low. But I love them now...Dan
     

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