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How does limited slip work?

cliffccliffc Posts: 9
edited March 1 in General
I recently noticed that when one rear wheel loses
traction like when you go over a mound of dirt.
One wheel slightly in the air and the other on
solid dirt. The wheel in the air spins and no
power goes to the wheel firmly on the ground. I
thought that limited slip would prevent this.
Service Manager at my dealer says this is "normal".
Does anyone know if this is true or not?
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Comments

  • FETZFETZ Posts: 51
    If he tells you that's normal for a limited slip to get power to only one wheel, then he doesn't know the difference between a limited slip and a regular differential (and shouldn't be working in the auto repair business).

    If this was a regular differential, this would be normal. But a limited slip differential should only let one wheel spin a little bit before it begins to transmit power to the other drive wheel.

    I wouldn't let them get away with giving you the old "that's normal" routine. I would either take it to another dealer for service, or escalate the problem through higher-ups (regional or district manager). Good luck.
  • bogiemanbogieman Posts: 12
    Amen Brother! You describe a standard rear action. With limited slip..... and I have it on my '98 F-150 w/ 4.6 L V-8....... as soon as the rear feels one wheel "outrunning" the other, it transfers power from the "free" wheel to the other side and you should feel this change..... or perhaps you do not really have a limited slip rear?
    Bogieman
  • cliffccliffc Posts: 9
    How do you "prove" that it is not working? I don't think it is working. I jacked up on rear wheel with a floor jack, put it in drive and the truck would move. The free wheel in the air just spun while the wheel on the ground just sat there. The Ford service manager claims that this is normal for limited slip. He says I'm thinking of locking differential. Have you tried jacking up one wheel to see if it will move the truck?
  • FETZFETZ Posts: 51
    I wouldn't use a "jack" method of testing it. It's a little dangerous with the potential of causing damage to the truck if it decides to take off. Take it in some mud or sand and have somebody watch to see if both wheels will spin. In a low traction situation like that you will definitely see BOTH wheels spin if it is working correctly.

    Another test would be to find a road with a muddy shoulder. Park with one wheel in the mud, and the other on hard pavement. Then nail the throttle. You should be able to take off without a problem if the limited slip is working correctly. A regular axle will just spin the tire in the mud and go nowhere.

    I had a Ford Ranger with limited slip that worked almost too well. The rear end would skitter around tight turns, because it wouldn't "differentiate" enough. And it would leave two equal length black rubber patches on the pavement if I burned rubber. If I got stuck in sand, both back wheels would be buried. It would allow little or no spin before kicking in the other wheel. Compare that to my F150 with a regular axle, that would leave only one rubber patch on pavement, and would only bury one wheel if I got stuck in sand.

    I have a Chevy truck now, with a locker. It will spin one wheel for a second or two before it decides to kick in the other wheel. And you can definitely feel it when it does. It allows much more spin than the limited slip does before transmitting power to the other wheel (from my experience).
  • FETZFETZ Posts: 51
    By the way, tell that service manager you want to talk to a mechanic, because it sounds like he's misinformed (to put it mildly).
  • smismi Posts: 13
    Which is better for off-road, limited slip or locking? Does anyone know which the Toyota T-100 4x4 has? If it is just plain then doesn't that realy make it a two wheel drive in the mud or sand(one in front and one in back?)Is there an aftermarket locker or limited slip for this truck?
  • FETZFETZ Posts: 51
    I personally prefer the way the limited slip works better. But I'm sure you will find differing opinions on that.

    I just visited the Toyota web site, and couldn't find any mention about what axle type the T100 has. They don't list options for that either (other than axle ratio).

    You're right about the regular axle on a 4X4. It is effectively only 2 wheels driving (one front, one rear).

    I have friends that have SR5 trucks, they came with the regular axle. One of them installed an aftermarket locker differential, and that made a world of difference on where he could go off road. I don't know if there are aftermarket kits for the T100. You'll have to ask around I guess.

    Good luck.
  • NuberOneNuberOne Posts: 29
    I am still not quite straight on this. I am going to order a new model '99 Chevy or GMC Full Size 2x4 pidkup with a tow package. There is no limited slip differential offered ... only a locking differential ($270 option). I will only tow a boat a couple times a year.

    Should I get the locking diff?
    Will it adversely affect gas mileage, performance, or handling?
  • KCRamKCRam Mt. Arlington NJPosts: 3,516
    That's the limited slip, #1. The manufacturers don't offer actual lockers. For true lockers, you need to go aftermarket. Add in the fact that each one has a different name for limited slip, and it's easy to see why a lot of folks get confused on this.
  • NuberOneNuberOne Posts: 29
    Will limited slip adversely affect gas mileage, performance, or handling?
  • cobra98cobra98 Posts: 75
    I would say that limited slip will not affect gas mileage (maybe in some minute theoretical calculation, but not in reality)

    Performance will be improved if your vehicle has enough power to spin a single wheel when accelerating (laying rubber). When both wheels put the power to the ground, you can launch quicker without spinning the single wheel.

    I would think handling should be more predictable as you come out hard (heavy gas) from a low speed sharp turn, because the shift of the vehicle weight in either direction will have the same result. In my F150, if I give it too much gas making a low speed sharp right hand turn, by back wheel (passenger side) wheel break loose and spin like crazy because most of the vehicle's weight is shifting to the front left. On the other hand, if I do the same thing making a sharp left, I can come out of the bend quicker because the right side of the truck is receiving the weight shift which puts more downforce on the right rear tire. My Cobra on the other hand (with posi-traction) lets me accelerate out of left and right turns the same.
  • NuberOneNuberOne Posts: 29
    I assume then that there is no appreciable vehicle weight increase when adding a locking differential.
  • cobra98cobra98 Posts: 75
    Your assumption is correct. I can't recall all the pieces in each of the rear-ends, but I know there are only a few more parts. No more than a pound I bet.
  • NuberOneNuberOne Posts: 29
    Thanks Snake
  • cobra98cobra98 Posts: 75
    don't mention it :-)
  • A limited slip diff will spin one wheel if there is no traction to one wheel as on Ice or up in the air. It will tranfer power to the stronger traction wheel only if the other wheel still has some traction left. Its a trade-off to allow cornering without dragging a tire vs an open tranny. Only a full locker will not spin a free wheel.
  • I'm about ready to order a '99 Silverado LT 2WD Ext. Cab. It will be used for around town, light hauling and boat/jet ski trailering as well as some hunting trips. Should I get the limited slip?
  • I would say "yes, get the limited slip". I'm wondering if anyone can give a valid argument as to when one should "not" get limited slip if it's available. The only valid reason I can imagine is that the individual might not think it's worth the $100 (or whatever it is) for the option.
  • After re-reading your post, I'd DEFINITELY recommend limited slip. Since you will be launching boats/jet skis you will want as much traction as possible. I've seen plenty of real slick boat launch surfaces.
  • In the source referenced above:Http://www.dynatrac.com/dyna4x4.html
    is the following discussion:
    "Many brands and styles of posi devices are available for different types of axles. They all share one
    common characteristic that helps them give more power to that wheel on ice we talked about earlier.
    Essentially posi units use clutches inside the device that press together when power is applied to the axle.
    This forces both wheels to try to spin at the same speed. However the main drawback to posi units is that
    they can only overcome a certain amount of traction difference between the 2 wheels. For example if we
    had one tire on ice as before and the other on dry pavement the posi would probably get us moving. But,
    if the truck was pointing up a sharp hill or the tires were in a small rut we would probably remain stuck.
    The reason is that even with power applied, the clutches would probably slip before the wheel on
    pavement would begin to turn"
    I hope this answers the original question. I am surprized that no one more experienced than I jumped in. Maybe its no worth getting flamed.
  • 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!
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