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Ring Gear Backlash for 12 bolt

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Mudzer, Feb 12, 2001.

  1. Mudzer

    Mudzer 1/2 ton status Author

    Feb 17, 2000
    Likes Received:
    I just set up my 4.88 this past weekend and I am a little concerned about my backlash setting. I got it to .015" of backlash and Randys Ring and Pinion recommends .006" to .010" for a 12 bolt. Should I worry about .005" or should I drain the oil, remove the pan, remove the locker, remove the axles remove the carrier and install a couple of shims? The axle is all setup and I have driven it the initial 15-20 miles. I would hate to remove the axles and stuff to get the new shims in there. Thats alot of work. But, if you think my 12 bolt will not last or could possibly break teeth off, give me your input. Randys Ring and Pinion is correct in saying .015" is a little high, because under a load, your pinion and ring gear actually separate from the forces generated by the pinion. If my setting is too loose, then I take a big chance of breaking teeth off. 9" Ford rearends are set up at .010" to .015" but thats because the pinion sets lower than a 12 bolt. They say the closer to the ring gear centerline, the tighter the clearances.

    Mudzer 1978/91 K5
    <font color=blue>www.mudzer.coloradoK5.com</font color=blue>
  2. ftn96

    ftn96 1/2 ton status

    Sep 26, 2000
    Likes Received:
    Nashville Tn
    what does your tooth pattern look like?

    Man that sounds shady to me. With this kinda precision, 5 thousanths can me alot. I know its alot of work, but, its better to be sure now than to have it sh_t on you latter.

    Will work for beer, parts and tools.
    90 Jimi,350/700R4/241/10bolts/4.10's/33's/4"
    <A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
  3. Executioner

    Executioner 1/2 ton status

    Feb 22, 2000
    Likes Received:
    Temp. Ft. Walton Beach Fl. home=Tucson, Az.
    It could be ok, I have see Richmond Gear ring and pinions get more than 80K miles, and B/L of 0.015 "
    in a 12 bolt, the spec. from R was 0.008-0.014 B/L, as ecthed in the ring gear.
    If your run a gear set made in France/India make sure that the pattern is the best you can get it, this will help
    insure a long life.
    If you plan on doubling you torque to that 12 Bolt, and using 2Low, be very carfull of any shock loads
    becuse the 12 bolt can't handle/take much.
    Good luck

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