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4.10 gears

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by therover87, Oct 15, 2001.

  1. therover87

    therover87 1/2 ton status

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    i have an 87 k5 and i just bought a dana 60 and a gm 14 bolt, im having a problem finding gears for the 14 bolt, what have you guys done, now its a 3.73 and i wanna change it to 4.10 i found the front gears in richmond but i cant find the rear gears. Also i was looking the powertrax automatic positive locking differential, is this a good choice for an everyday driver or should i go with the no-slip powertrax differential, thanks.
     
  2. CaptCrunch

    CaptCrunch 1/2 ton status

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    Rear lockers/posis choices are like asking about which ift brand... tons of different opinions. The 14FF is pretty limited in selection though. If you get snow and ice I would forget about anything put a posi (I'd recomend looking into the Eatons and detriot trutracs... not sure if either are avalable for the 14BFF). Also they will be much better for tire wear and street driving... but you will want to make sure you have an e-brake so you can "help" them lock up.

    I personally am gonna keep my rear open and just go an ARB in the front since it is a daily driver and I see snow. Most of my oofroading leaves my rear wheels on the ground anyways.

    Check these guys out... they have a great tech line and service.

    http://coloradok5.com/gallery/captcrunch
     
  3. txbartman

    txbartman 1/2 ton status

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    For the R&P, you also might want to check out Randy's Ring & Pinion (My Jimmy with all her projects!
     
  4. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Most aftermarket gear manufacturers should offer 4.10, 4.56, 4.88, or 5.13 gears for the 14 bolt. I've never heard of anyone having trouble finding them before.

    Concerning going to 4.10 gears, I'm assuming since you are going with the Dana 60/ 14 bolt combo you are planning on big tires, correct??? Also you have an '87 Blazer, so assuming it's an automatic it will have the 700r4 with overdrive?? Just something to think about but you might be happier with lower gears if this is the case. There's not much difference between 3.73 and 4.10 gears.
     
  5. txbartman

    txbartman 1/2 ton status

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    I'm not sure what all the fuss is about 4.56 gears with an overdrive transmission. According to my math, you calculate your RPMs ata specific speed with the following formula:

    (MPH x Gear Ratio x 5280 x 12) / (Tire diameter in inches x Pi (3.1415) x 60)

    This will give you RPMs at a 1:1 tranny ratio. Since the 700R4s overdrive is .7:1, you would simply multiply the result by .7 to determine the final RPM for an overdrive tranny.

    According to that, an non-OD tranny would be running at 2930 RPMs at 65 MPH. A OD tranny would be turning 2051 RPMs at 65. This is based on a 35" tire with a nominal diameter of 34". If you went to a 4.10, an OD tranny would be turning only 1844 RPMs at 65 in OD. That is a bit low in the power band to keep the vehicle at highway speed. And keeping RPMs too low and gear shifting causes more heat for the 700. Bad, bad thing.

    Brian
    Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!
     

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