Exactly what is the point of a "Limited slip" rear end?

[entropy]

People think their limited slips arent working because they dont truly understand how it work. You do NOT need to have zero traction on one tire for it not to work.

It is a torque multiplier unit. The tire that has the least amount of traction decides if the vehicle will move or not. How? whatever torque it has available that's providing traction gets multiplied and sent to the other tire. It gets multiplied by about 3 at the most. If you need more than that, it won't work.

A tire in the air situation has 0 traction. The tire on the ground gets nothing. A tire on ice could have 0 or close to 0 traction. Remember, if the torque bias between both tires is more than 1:3. It wont do nothing.

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[entropy]

Thanks very much for all the responses, some of which really took you guys some time to write. I appreciate the effort.
I guess I do not have BLD, just LSD, which, it seems to me is pretty much useless unless it's in a GTO and you want to do a burnout on dry pavement. And even with BLD, the guy was stuck in what was not very much snow. Kind of pitiful to watch. Maybe my '97 Wrangler was better in the snow because the tires weren't as wide.

You do have BLD.

If the guy in the video had a rear locker and an open front he would have been stuck anyway on that situation. Even when your LSD is able to provide torque to the tire that needs traction doesn't mean you'll get out.... people get stuck with lockers too.

Use tires that have better grip on ice if you want your LSD to work on ice. Good set of winter tires with studs will do the trick.

You also got a dana44 rear axle. That alone is worth the expense of the limited slip option.

If you want to have the ability to get unstuck on any snow situation, get a winch and learn how to use it. Traction boards can also be a huge asset if you have a limited slip. Limited slip is designed more for on the move traction than to get a static vehicle unstuck. Lockers are designed to get the most traction out of a vehicle on slow offroad situations.

 

[bwright1818]

Thank you for the reply. I am pretty sure studs are illegal in Massachusetts where I live; but I like the idea of traction boards. As for the winch, it might be an idea for me.... Although where I got stuck in the snow last time, it was a real long way to anything like a tree to attach it to. Maybe a boat anchor might have helped!

 

[WilhelmSR]

 

[6.2Blazer]

Well, geez, I hope it's not worn out yet. I only have 17K on it in three years!

Maybe the air is a little extreme but I don't see why ice wouldn't work. Let's say that one wheel was on ice and I wanted to turn it by hand. I seriously doubt that I could do that, because even ice has some friction to it with a decent part of the Jeep's weight sitting on it. Right?

The difference between a tire on dry asphalt versus a tire on ice is still very extreme. Granted you wouldn't be able to grab the tire sitting on ice and spin it by hand......but the amount of torque you would be capable of exerting on the tire by hand is tiny compared to what the engine and gearing provide. A 3.6L is rated at 260 ft-lbs of torque, times 4.7 for the first gear of the automatic trans, and then at least 3.45 times in the differential. That equates to over 4,200 ft-lbs of torque. Sorry, but unless you are Superman a person could only apply a small fraction of that trying to grab a tire and spin by hand.

Overall you have to remember that the L is LSD stands for limited, which means it simply limits the amount of spin between the two tires but does not completely get rid of it.

 

[Norvak]

I love an LSD. I had one in my past 2 rams and now in my Willys. The one in my Willys is super sensitive. I take a right hand turn on a wet road at 10mph and I'm skipping along. However it does work great when I'm driving through the muddy cattle pasture.

 

[bwright1818]

I had some time and went back and watched the You Tube video. I understand now, how it's supposed to work, I think. The more force that is applied to the gears, the more they want to try to separate and so the more force is applied to the clutch packs. They ought to call it a Catch 22 Differential. Still, with the supposed preload spring in there, you'd think that would be enough pressure on a clutch pack to try to knock it off a sketchy little jack. Anyway, so now enter anti-lock brakes: If one wheel is on the ice and the other is on pavement, and I apply the brakes, the anti-lock feature should apply brake force to the slipping (turning) wheel and NOT apply brake force to the wheel that is NOT turning on the dry pavement (essentially "locked.") So by applying light brake pressure, I am loading the gears enough to compress the clutch pack on the non-slipping side, and I should move. Have I finally got this right? If so, the traction control switch: It is normally functioning and if I depress it, it turns the function OFF? Have I got that right? Or is that backwards?

 

[bwright1818]

The more I think about it, the more I realize how little I understand. With anti-lock brakes, and you sitting on a flat surface, not moving in the first place, then in basic theory, when you put your foot on the brakes, no brakes are actually applied. That can't be right. What's the catch, there? The brake control must have to see some sort of speed, to work?

 

[Hit&Crawl]

Limited slip differentials provide you more control by using the wheel on the pavement to make up for a lack of grip on your wheel in the frozen puddle. Due to the fact that a limited slip differential makes better use of engine power, it is important to ensure that at least one of your Jeep's wheels has adequate grip. This is why you often see individuals using tire traction mats.

 

[Jtclayton612]

The more I think about it, the more I realize how little I understand. With anti-lock brakes, and you sitting on a flat surface, not moving in the first place, then in basic theory, when you put your foot on the brakes, no brakes are actually applied. That can't be right. What's the catch, there? The brake control must have to see some sort of speed, to work?

anti lock brakes are ABS, we’re talking brake lock differential, or BLD, and yeah it takes some wheel spin to achieve and isn’t activated by you pressing down on the brake, it’s a computer controlled system. Two footing it and keeping enough brake pressure while giving it gas is used while off-roading though.

 

[oldcjguy]

I had some time and went back and watched the You Tube video. I understand now, how it's supposed to work, I think. The more force that is applied to the gears, the more they want to try to separate and so the more force is applied to the clutch packs. They ought to call it a Catch 22 Differential. Still, with the supposed preload spring in there, you'd think that would be enough pressure on a clutch pack to try to knock it off a sketchy little jack. Anyway, so now enter anti-lock brakes: If one wheel is on the ice and the other is on pavement, and I apply the brakes, the anti-lock feature should apply brake force to the slipping (turning) wheel and NOT apply brake force to the wheel that is NOT turning on the dry pavement (essentially "locked.") So by applying light brake pressure, I am loading the gears enough to compress the clutch pack on the non-slipping side, and I should move. Have I finally got this right? If so, the traction control switch: It is normally functioning and if I depress it, it turns the function OFF? Have I got that right? Or is that backwards?

You are pretty close. Anti-lock braking doesn't come into effect. Applying the brake pedal will apply braking force to all wheels, but that's ok because it will still create that dynamic load you need. The BLD (Brake Lock Differential) system is controlled by a computer and will automatically apply the brakes to a single wheel (the one with the least traction) making the LSD work even better by creating some dynamic load on a single axle.

 

[AcesandEights]

... They ought to call it a Catch 22 Differential.

Joseph Heller was a very good writer, but I don't think he was thinking about the limited slip differential when he wrote Catch-22 (one of my favorite books).

...Still, with the supposed preload spring in there, you'd think that would be enough pressure on a clutch pack to try to knock it off a sketchy little jack...

You don't want both wheels turning with power to both in certain situations. Snow covered highways, or rain, are a couple of places you really want to limit the power transfer, and you will actually maintain better control with power (torque) applied to one wheel. When both turn in a poor traction scenario, it will break one of the tires loose. That can cause you to slide. So, it's the reason a limited slip isn't a locker, or why the pre-load isn't more effective. You want the wheels to turn at different rates (around corners), or with different amounts of power applied (especially when cornering in low traction situations). A limited slip helps you when you're off road, but is "limited" so that it doesn't cause issues on road. It's a compromise, on purpose, or intentionally, so you wouldn't be able to knock it off a sketchy jack with the stock preload (it'd send you sliding sideways in the rain).

 

[Rubigone]

I’ve been in a similar situation to you and i don’t have an lsd, but the bld took me right out. Within a second i could feel the spinning wheel locking up and traction going to the other one. Could it be that jeeps with lsds have less agressive bld?

 

[JJM]

OK but the listing says nothing about a "limited slip differential"

Dana M220 Rear Axle
Anti-Spin Differential Rear Axle

Same thing?
Is that Jeep's terminology for an LSD?

 

[oldcjguy]

OK but the listing says nothing about a "limited slip differential"

Dana M220 Rear Axle
Anti-Spin Differential Rear Axle

Same thing?
Is that Jeep's terminology for an LSD?

Anti-Spin is Jeep's name for a limited slip differential. All the manufactures put their own spin on the name. lol see what I did there

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