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How to tell Posi or locker? or open diff...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rocko, Jun 21, 2001.

  1. rocko

    rocko 1/2 ton status

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    Okay.. I just popped my diff covers.. to confirm I have 3.73's. I do.. the ring is stamped 41:11 .
    Now.. I think I have a limited slip unit inside.. How does one tell?
    I know on wet roads... if one tires starts to spin.. the other one gains traction and away I go.. it does real well on slick roads..
    Now what does one "limited slip" visually look like? Any one have pictures? I've looked on 4lo.com and ring-pinion.com
    But no "pictures for dummies".. [​IMG]
    Any suggestions, tips, pointers.. would be greatly appreciated..
    Thanks in advance.
    Rocko.

    The unit inside my rear axle it's a carrier with 4 smaller gears connected by a center rod.. the top small gear looks a little worn.. but the actual pinion gear and ring gear have no wear on them at all... it looks like pitting marks on the top little gear.. is this normal?

    A well armed society is a polite society. <A target="_blank" HREF=http://www.rocko.rockcrawler.com>http://www.rocko.rockcrawler.com</A>
     
  2. POWERMAD

    POWERMAD 1/2 ton status

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    rocko
    The easiest way to tell providing that it is operational is to jack up both rear tires and spin one of them. if both wheels turn in the same direction then it is posi.
    As far as pix this is all i can come up with.
    <A target="_blank" HREF=http://www.ring-pinion.com/product_info/posi.htm>http://www.ring-pinion.com/product_info/posi.htm</A>
    If you can see into the carrier and if it is an open diff it will have just spiders inside of it.
    A posi unit will have springs and such inside the carrier depending on the make of the unit.


    my truck's not dirty, it's earth tone paint
     
  3. HarryH3

    HarryH3 1 ton status Author

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    That trick doesn't work for all posi diffs. I know that neither the Eaton Gov-Loc or the Zexel Torsen behave in that manner. Wtih either of those diffs, the other tire will spin backwards, just like with an open diff.

    I'm not sure, but a Tru-Trac may behave like an open diff with this "test" as well.

    <font color=black>HarryH3 - '75 K5</font color=black>
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  4. POWERMAD

    POWERMAD 1/2 ton status

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    Thanx fer the info
    Ron... learning new tricks everyday!

    my truck's not dirty, it's earth tone paint
     
  5. HarryH3

    HarryH3 1 ton status Author

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    That's what this place is all about! [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://www.angelfire.com/super/ThunderTruck>http://www.angelfire.com/super/ThunderTruck</A>
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  6. BOWTIE

    BOWTIE 1/2 ton status

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    The Trutrac I had in my Diff would make my tires rotate in the same direction. As far as what you got, Rocko, can you tell if there are any clutch packs in you carrier? If so I believe it would ba a gov-lock. And if you do you will need a limited slip additive for your gear lube. Hope this helps and please correct me if I'm wrong.

    Ric

    "Wheel hard or go home."
     
  7. HarryH3

    HarryH3 1 ton status Author

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    Interesting! I'll have to file that away for future reference. I've had Gov-Locs and have a Torsen in my S-10, so I've seen first hand how they behave. Since the Tru-Trac uses worms gears and such, somewhat similar to the Torsen, I wondered if it would behave like an open diff in that test as well. The designs aren't exactly the same and I think that the Tru-Trac actually jams the worm gears against the case a bit, so it makes sense that it would transfer rotation through to the other side.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://www.angelfire.com/super/ThunderTruck>http://www.angelfire.com/super/ThunderTruck</A>
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  8. Executioner

    Executioner 1/2 ton status

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    Maybe when they are new(just installed), but after break-in, they are designed to act like an open diff.
    there is no(zero) torque bias .
     

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