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Is my diff supposed to do this?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Can Can, Sep 17, 2001.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Tonight I got a flat tire(rear driver's side) on the way to the ol' fishing hole. I jacked up the rear driver's side and put on the spare. While I was taking the flat off I realized that I could spin the rear driver's side wheel about an 1/8th of a turn back and forth with the passenger side rear wheel still on the ground. Is this supposed to happen with a Limted Slip 10 bolt? I don't have any problem with the rear end that I know of......



    <font color=blue> WE WILL NEVER SURRENDER<font color=blue>
     
  2. Pugsley

    Pugsley 1/2 ton status

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    It's normal - Limited slips have a little room to ratchet before they lock up the wheel. That's the actual "differential" action - allowing one to freewheel while the other turns, so you can go around corners without spinning tires and/or breaking something.

    Special thanks to those lost from IAFF Locals 94 and 854 - You shall never be forgotten
    <a target="_blank" href=http://pugsley.alloffroad.com>pugsley.alloffroad.com</a>
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    What kind of "limited slip"? A cone type (auburn) should I guess, since it is "threaded" A GM actual limited slip (cone type like the auburn is pretty rare stock) should NOT do this, nor should the Gov Lock. Even turning the wheel slow it locked up? Gov lock (which is what should be in a truck 10 bolt stock) should free wheel indefinitely, and a typical GM limited slip (non gov lock) should be COMPLETELY LOCKED TOGETHER 100% of the time. They do not unlock, they do not ratchet, they do nothing but SLIP when one axle needs to differentiate, say in a corner. No offense, but that is the way it is, and the way it has ALWAYS been with GM.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  4. Hossbaby50

    Hossbaby50 3/4 ton status

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    The Auburn in My Jimmy won't turn with one wheel down unless you work pretty hard to it. I am not sure about the gov lock though, mine blew up before I had the chance to test it.
     
  5. Executioner

    Executioner 1/2 ton status

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    Could you please explain more about the Gm limited slip(non Gov lock) ?
    With one wheel/tire in the air, other wheel on pavement, and tranny in park(i.e. rear driveshaft held in postion) ?
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    No problem. Heres the situation: Non cone type, properly operating. (not worn out) You are trying to turn raised wheel by hand. Tranny in park. Wheel will not turn.

    now, since we already went through this before, and you *tried* to make an ass out of me, (with a snide comment)without knowing what *you* are talking about, I am assuming you are trying the same thing now. So, if you (or anyone that doubts this) are in possession of a GM Service Manual, or even a Haynes, turn to the section on limited slip diffs. You will see that to properly test a limited slip differential, PER GM, you have to use a device to measure the amount of force required to make the axle "slip" against the clutch/spring setup. If it slips UNDER (off top of my head) 35ft lbs, its worn out. 40ft lbs is if its new IIRC.

    Sure, you can overcome the spring force, thats why they are great for cars. They are bad for trucks because they will slip even when you need them not too...anytime the "grip" of one wheel overcomes the other by that factory set preload, it will slip.

    So in your situation that you described, if you applied more force than the preload setting, you CAN force the wheel to turn.



    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  7. Pugsley

    Pugsley 1/2 ton status

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    I went out and tried it on mine (OEM limited slip) - there's about 20-30 degrees of travel with very little resistance. I didn't test it with a torque wrench, but considering the mechanical advantage of the tire, and accounting for gear wear (they are 16 years old), I'd say it's normal/within normal limits.

    Special thanks to those lost from IAFF Locals 94 and 854 - You shall never be forgotten
    <a target="_blank" href=http://pugsley.alloffroad.com>pugsley.alloffroad.com</a>
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    So are you talking OEM 10 bolt truck limited slip (Gov-Lock) that does this? I'm gonna have to jack mine up on one wheel and see what happens. I *know* what happens when both are off the ground, and what happens when you spin one of those wheels by hand quickly, but never tried a gov-lock with one wheel on ground one off.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  9. Pugsley

    Pugsley 1/2 ton status

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    Yup - 10 Bolt Gov-Lock.

    Special thanks to those lost from IAFF Locals 94 and 854 - You shall never be forgotten
    <a target="_blank" href=http://pugsley.alloffroad.com>pugsley.alloffroad.com</a>
     
  10. Executioner

    Executioner 1/2 ton status

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    Just trying to understand you !
    The last sentance, can you look it over, something just does not seam right.
    Thanks alot
     
  11. Thumper

    Thumper 1/2 ton status

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    Ummm just a question... were you in 'Park'? If you were in park, with the other wheel on the ground, the tire will only turn until it takes up all the driveline slop up to the tranny. Regardless of what type of locker you have it wont turn in park. But it will move a bit back and forth. Mine moves a bit, as far as the tranny will let it turn.
    Also, I have a Tru Trac in my 12 bolt. With one wheel off the ground, in Neutral, the wheel turns by hand relatively easily, but if I give it a hard spin, it will try to engage the other side. With both tires off the ground they turn opposite directions by hand, but if I give it a good hard spin, it will start to lock the other side and turn it the same direction. My old Gov-Lock worked the same way.

    Sounds OK to me.

    Mike


    <font color=blue>Thumper
    85 Fullsize Jimmy
    [​IMG]
    <font color=red>Aint Skeered!! </font color=red>
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    "So in your situation that you described, if you applied more force than the preload setting, you CAN force the wheel to turn. "

    If you can get enough leverage, with one wheel on the ground, you CAN turn one axle even on a posi differential, since spring pressure (the internal carrier springs) is the ONLY thing keeping the left and rear axle locked together. Is that clearer? Posis are good BECAUSE they can slip when cornering. Thats also the reason they are bad in extreme situations, because you may get one wheel "bound up" tight enough (stuck against a log for example) that it ceases to spin, and the other spins worthlessly.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  13. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    UMMMMMMMMMMMM........So is my diff supposed to allow this or not???

    I still don't feel that anybody other than Pugs gave me an answer......[​IMG]



    <font color=blue> WE WILL NEVER SURRENDER<font color=blue>
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    Is yours a stock unit or something someone has thrown in in the past? (which I need to know, because I only have a gov-lock in the truck, and a true GM limited slip diff in my cars 10 bolt8.5") I haven't answered your question because I haven't had time yet to jack up one rear wheel of my gov-locked 10 bolt. Apparently its working fine, so I just need to get a jack under it and try spinning it.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  15. Executioner

    Executioner 1/2 ton status

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    Hummmm, lets see the tire is connected to the wheel, is connt to the axle, is connt to the side gear, is connt to
    the spider(pinion) gear, goes through the cross shaft(pinion shaft), is connt to the case, is connt to the ring gear,
    is connt to the pinion, is connt to the driveshaft...............
    Do you see what I am getting at ?
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    No I don't see what you are getting at. : )

    First off, the pinion shaft is static. it does not move. It keeps the pinion gears in place, and keeps the axles from moving in far enough for the c-clips to fall off

    The clutches keep the side gears "locked", so both the right and left side gear spin at the same time, turning the pinion gears at the same time. Since the clutches are the not actually locked (they are held by spring pressure once again) they HAVE to slip when enough force is applied to one side.

    There is no physical, mechanical locking of the wheel all the way to the driveshaft, if thats what you are getting at, with a limited slip diff. heres a pic: <a target="_blank" href=http://www.torquecontrol.eaton.com/graphics/shared/limslip2.jpg>http://www.torquecontrol.eaton.com/graphics/shared/limslip2.jpg</a>
    Dorian
    My tech/links page: &lt;a target="_blank" href=http://www.dorianyeager.com/index2.html&gt;http://www.dorianyeager.com/index2.html&lt;/a&gt;
    No anti-theft measures on your truck? No pity when its stolen<P ID="edit"><FONT class="small">Edited by dyeager535 on 09/19/01 04:05 PM.</FONT></P>
     
  17. Executioner

    Executioner 1/2 ton status

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    Something still don't sound right ! If the side gear is turning, so must the pinion gears...........right ?
    Becuause the ring gear/case is stationary !
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

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    Man! Gonna have to write or find an FAQ on this! (and I looked : )

    Even on an open diffential, straightaway, the pinion gears nor the side gears spin. (which is why welded rears still work fine most of the time) Can you see in your head the side gears turning the same direction together? Now imagine the pinion gears that mesh with the side gears. If both side gears are turning the same direction, at the same rate, the pinion gears don't move, right?

    Now, turning. One axle HAS to turn slower than the other. Once that starts to happen, the pinion gears HAVE to turn, to allow for the different axle speeds. Make sense still? Do you see the pinion gears rotating now that one side gear is turning slower than the other? (not to make sound dumb, its easier to "imagine" the workings in your head)

    The ONLY difference between an open diff and limited slip, is that the springs in the limited slip diff are trying to KEEP the two axles, and thus side gears, turning at the same rate, keeping the pinion gears from rotating. Once one axle exceeds the spring pressure, (as in a turn) the pinion gears start working, and the whole assembly acts the same as an open diff.

    And you should be able to see that offroad, with large tires running up against large objects, with one wheel off the ground sometimes, limited slip would not work as well as a locker, and why lockers ARE better off road for the most part.

    Now, does that make sense?

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    Sorry! Bad link before!

    http://www.dorianyeager.com/index2.html
    No anti-theft measures on your truck? No pity when its stolen
     
  20. dyeager535

    dyeager535 1 ton status Premium Member

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    Ok, jacked my truck up tonight. G80 diff in visually good shape. (its a Gov-Lock in other words)

    With one wheel off the ground, no e-brake, tranny in NEUTRAL, the tire would spin freely either direction, as would the driveshaft. I half heartedly tried to spin the tire in this situation to see if it would lock, it would not. I was also afraid the truck would start rolling down the driveway if I put enough force in it : )

    Same situation, with tranny in gear. Wheel turned maybe 3 inches and stopped. Either direction. Sounds like you're ok if the tranny was in park or gear if manual.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     

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