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14bff gear install, specific questions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by RodeoRob, Oct 21, 2002.

  1. RodeoRob

    RodeoRob Registered Member

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    gear install experts, i was wondering if you can help me out with a few questions i have. I've got a few gear installs under my belt, but i don't consider myself a pro or even feel that comfortable with it.

    1. my 14bff gear is stamped with a backlash of 0.08. Now that seems a little much as i thought most gears were in the area of 0.008 - 0.012 including my D44 that i installed which was stamped with 0.008. I wouldn't think there could have been a 'typo' when stamping my gear?!

    2. what causes backlash to be different in as you go around the gear? I understand you won't be able to read backlash in the same spot everytime which could account for some different readings, but i'm talking like no backlash on one side of the gear and 0.015 on the other. the pinion not sitting right and ring gear not sitting on the carrier right is all i can think of??

    i have a set of 5.13's i'm now installing into my 14bff. pattern looks okay to me, but then again, i'm a novice. symptoms are at about 60mph and above, when i let off the accelerator, i get a fairly load noise and vibration from the rear of the car. As soon as i touch the gas, it goes away. This would tell me the coast pattern is off, right? Could question #2 have to do with this (i assume so). I've gone back and tried to set it up a second time, and had the same results. can someone offer me some guidence?

    Thanks,
    -Rob
     
  2. jjlaughner

    jjlaughner 3/4 ton status

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    I'm in no way an expert at gear installs. I would guess that the readings going from 0-0.015 are shifts in the bearings. Maybe not pressed on right or the area where the bearings sit may be worn. Second the noise when you let of the gas may be a u-joint. When you hit the gas it adds pressure and that takes out the vibe and makes the sound go away and when you let off a little it slack allows the u-joint to move around. I would say grease the u-joints real good see if helps, otherwise replace them.
    I'd wait till some others post in here with their ideas before you take my word on it, but thats my 2cents anyway. I've had the u-joint thing happen to me before though. If it was the other way around, it makes noise during accelaration and doesn't coasting, theres water in the cap! I almost replaced a couple ujoints making the same noises but it through me off because it was under acceleration not coasting, but the noise and the reactions of the truck were the same a bad u-joint. Just a side note. good luck, J
     
  3. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> I've seen recommendations that the backside of the ring and the seating surface on the carrier for the ring be touched up with a wet lapping stone (or something) before putting the gear on. A tiny peice of metal stuck between the gear and carrier could also probably cause a .015 variation I would think, it's really not all that much inthe big scheme of things, but it's alot for gears... </font color>
     
  4. POWERMAD

    POWERMAD 1/2 ton status

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    About the backlash.
    The gearman at work sets his up with the minimum of .001" per inch of ring gear.
    Ex 10.5" ring gear--.010" min backlash.
    When I welded up the spiders I check the backlash and it was at .018".
    The pattern looked fine so I put it back the way it was.
    I asked him about it the next day because I thought it too excessive. He said it was fine.
    He has been building gearboxes and diffs for 30 years, I take what he says to heart.
     

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