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How does limited slip work?

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Comments

  • In regards to the desirability of a limited slip in the above referenced web site:Http://www.dynatrac.com/dyna4x4.html is this interesting opinion.
    "Most posi units are designed to try to keep both wheels turning, but still allow one wheel to turn slower
    than the drive shaft in order to allow the vehicle to corner smoothly on the road. For better traction a posi
    unit is always superior to the open differential. They usually require a special lubricant or additive in the
    gear oil to function correctly and will become less effective as the clutches wear out. However, most can
    be rebuilt for a reasonable cost. Keep in mind that a posi in good condition will likely cause the vehicle to
    fishtail and slide to the outside of a turn on very slippery surfaces like snow or ice, so use caution under
    these conditions. There is no substitute for prudent driving."
    I have a 95 Jeep cherokee with a limited slip and haven't noticed any fishtailing but then I did't know until now that it was a possibility and my memory is not that good. 8:) happy four wheeling.
  • I have a 1998 Chevy 1500c pickup. I like my truck and it's small v-8 for towing my boat, but have a traction problem at several ramps I use. Am thinking about trading it in for a 4x4 with a locking rear end, but after reading these posts, I am wondering if I can get an aftermarket locking differential installed, and whether it is likely to work well. Any experience with this, and what kind of costs might it entail and where to look for the kit? Thanks in advance.
  • polsenpolsen Posts: 25
    Four Wheeler Mag listed the aftermarket sources on their on line Mag. See http://www.fourwheeler.com/gear/srcgd98/index.html
    You can also look up your local 4x4 shop in the yellow pages. My town (Salt Lake City) has several 4x4 equipment shops including Mepco and several shops who install and switch axles. Also search the internet through your favorite search engine for "4x4" or "four wheeling" or "locking transmissions".
  • Locking-axle is a misnomer. What they are referring to is a limited slip differential carrier. The carrier is the part that the big ring gear mounts on. Inside it are 4 planetary gears that connect to each axle and the drive pin. When the wheels are turning at the same speed, the planetary gears are stationary. But when one wheel turns faster than the other, the gears begin to rotate in opposite directions. If you jack up the rear end, turn one wheel by hand and the other will turn opposite on a regular differential. On the locking, same but you will feel some resistance. Now start the engine, put it in gear, wheels turning slowly (still on jackstands).If you grab one wheel by hand and stop it, the other will keep turning if you have a regular differential. But if it tries to rotate you with it, you have the locking. But the difference is only slight, because the clutches that make it possible are tiny. The limited slip carrier is just like the regular kind, except that it has tiny friction clutches, which work to minimize the tendency of of the planetary gears to rotate in opposite directions. If you don't have one, no big deal really. But if you want one, you just replace the carrier at about $325. The Chevy GMC dealer you could get to do this for you, parts and labor $650 I'm guessing. Axle shops can do it also, but be careful. You get what you pay for. If you use the Chevy (Auburn) differential instead of aftermarket, you won't need to re-shim for correct backlash, key to quiet running. Locking axles are useful on ice, or a slippery boat ramp, but don't expect too much. When you overcome the friction of the clutches, the planetary gears will counter-rotate, and one wheel will spin wildly while the one with the good traction sits idle, just like a regular axle. The key to remember is that your traction is no better than lesser of the two wheels. One wheel on ice, one on dry cement, both might as well be on the ice. Locking axle only slightly better. Same thing on the front end. Four wheel drive is really just one driving up front, one in back, but it can be either one, with traction only as good as the traction of the lesser.
  • tungletungle Posts: 56
    After I visited the dynatrac web site, I wonder
    which axle (GM10, 12, 14, or ???) are being used
    on the '99 Sierra/Silverado. Anyone has any info
    on this?
    Thanks,
    Tung
  • dave40dave40 Posts: 582
    I was told the Limited Slip does not work over 10 MPH on the Chevy C/K trucks. My 96 worked fine for the first 5000 miles then it was useless. Took it back to dealer a few times they said it was fine. But it wasn't. Hope the new 99s last longer, I heard there using better longer lasting carbon fiber plates this time. Time will tell!
  • markbuckmarkbuck Posts: 1,021
    tungle - I think 10 bolt GM on the 1/2 ton. Supposedly they upgraded the lim slip mechanism for 99.
    dave40 - drove a new Silverado 5.3 with lim slip with only a few miles. Drove around a snowy parking lot at speeds up to 40. Truck was plenty loose at higher throttle settings, and both rear tires would break loose. Maybe it worked so good 'cuz it was new.
  • Jeremy,
    There is another option to the limited slip. I believe it is ARB and others I am sure, that make a "locking" differential. The advantages to the "locker" are the wheels turn together, no clutches to wear out, and you only engage it when you want it, ie. climbing up a slick boat ramp. The disadvantages would be, additional hardware to engage and disengage it, you have to "turn it on" for it to work, it is not just waiting around for a wheel to start slipping. Cost should be comparable if costs in the previous posts for limited slips are close.
  • jburgosjburgos Posts: 2
    Would a rear locking differential help traction in the snow in a 2WD pickup?
  • quadrunner500quadrunner500 Posts: 2,728
    It would help, but it's effect is marginal. As long as you aren't expecting more than a little assist pulling away from the curb, or gaining traction while moving away from a stop light. But if one wheel is in a hole, and another is on smooth ice, forget it!
  • clark7clark7 Posts: 4
    I have an older Toyota Landcruiser (but I have a new Sierra 4WD Ex Cab coming soon). Recently in my Toyota, I got in a situation where one of the rear wheels had essentially no traction. Both front wheels and the other rear had good traction on dry ground. When I applied power, the rear wheel with no traction would spin, the transmission/transfer case would make a ratcheting noise, but no power was transferred to the front wheels. Based on previous posts, I can understand not getting drive from the rear axle, but shouldn't I have gotten drive from the front with both wheels having good traction? Could I have a problem with the 4WD system?

    I know that on more recent Landcruisers and some other 4WD vehicles, there is an option for a "locking center differential". Sounds like that might have forced power to the front wheels, even with the rear wheels off the ground. So, my other question is, does the autotrac system in the new Sierra/Silverado have what amounts to a locking center diff? If not, how do they handle this type of situation?
  • tnt2tnt2 Posts: 115
    jburgos ... A locking diff would give additional traction, but it also makes the truck "push" in turns. This goes more for "air lockers"(that are engaged) than "auto" lockers, unles you punch the gas in a turn. With auto lockers you will also hear a ticking noise coming from the diff, there are levers that click on teeth as you drive and engage when put under hard pressure, thus locking your diff and providing full power to both wheels.
  • markbuckmarkbuck Posts: 1,021
    Your Landcruiser is broken. Get the transfer case and/or locking hubs looked at.
  • clark7clark7 Posts: 4
    Thanks. Guess I was afraid there might be something wrong. I'm still curious as to how the autotrack system works relative to a locking center differential.
  • nevvic1nevvic1 Posts: 3
    I plan to get a Ram v-10 with a 3.55 axle ratio. I have heard that there are some problems with the limited slip differential in Rams with this ratio. Any input on this would be appreciated.
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