Limited Slip Differentials

[VetteOwner]

its a ranger just like my s10, while torque steer should never be in the same sentence as either vehicle it does exist

also i dont know about the ranger but my s-10 the gastank is on the drivers side so you get alot more weight on one side.

also whos to say you came off the bump straight(ive hit those angled bumps and it will make the backend go out)

also ive noticed if i just gun it in a straight line the backend inevitably swings out to the left (on level pavement) sloped pavement well it swings toward the ditch

so yea im sure it could, my truck does it with an open diff (i think it starts to slide when i give it enough gas and such to get both wheels spinnin)

[theholycow]

Originally Posted by trollbait

A little off topic, but could LSD cause the rear end of a vehicle, going straight, to whip out to the side? This has happened to me several times in the ranger when hitting a bump just right while applying a gas. I thought it was just one of the quirks of a light backside and solid axle. After reading up on LSDs, now I'm not sure about that.

That's not off topic, that's exactly what this thread is about, and it's exactly what I (and others) have been saying here. With an open diff you're far less likely to get that sideways movement than with a LSD.

[dieselbenz]

Originally Posted by theholycow

That's not off topic, that's exactly what this thread is about, and it's exactly what I (and others) have been saying here. With an open diff you're far less likely to get that sideways movement than with a LSD.

Maybe on an body on frame pickup with leaf springs and a solid axle where 2/3 of the weight is on the front tires. We need to differentiate between cars and trucks. In my experience installing an LSD only improved traction and stability especially on slippery surfaces.
You shouldn't see ANY sideways movement with an independent rear suspension with or without LSD unless you're purposely trying to induce a slide while cornering.

[theholycow]

I don't understand how suspension should affect it. If you are spinning both rear tires, they are going to lose lateral traction no matter what suspension you've got, right?

[trollbait]

Vetteowner has stated he's had an open diff S-10 kick out like my Ranger. My friend has had the same thing happen also, I need to find out if it was open or LSD. So I think my issue is caused by original suspect, where suspension does matter.

I've heard it referred to as axle hop (or warp or wrap). While power is being applied to the wheels of a RWD, solid axle vehicle, and it hits bump that allow the drive wheels to lose contact with the road, the forces on the drive train can twist the axle just enough that the rear wheels are no longer straight when they gain traction again. This causes the rear to kick out. Of course it will be more likely in a small, empty pickup. In my experience, this kick out is instantaneous, and auto corrects just as quickly. Leaving me going the the direction I was going before without deviation.

It doesn't occur with an independent suspension because the movable joints don't transfer any twisting from the driveshaft to the wheels.

[dieselbenz]

Originally Posted by theholycow

I don't understand how suspension should affect it. If you are spinning both rear tires, they are going to lose lateral traction no matter what suspension you've got, right?

With IRS, LSD and descent front/rear balance you should be able to get traction before spinning both rear tires. The rear tires will have at least some negative camber which will help keep the car from moving sideway even when you're spinning the tires at a standstill and you don't have the problems of axle hop and twist. IRS doesn't resolve every traction issue but with an LSD it can provide very good traction. If you're trying to floor it on ice from a stand still you'll still be just as stuck as any other car.

Originally Posted by trollbait

It doesn't occur with an independent suspension because the movable joints don't transfer any twisting from the driveshaft to the wheels.

bingo

[theholycow]

I have gotten my open diff pickup to kick out sideways from power applied, plenty of times. However, when talking about slippery road conditions, it's far more common with the limited slip.

There's a multitude of causes of a sideways kick.

One could be axle wrap (and frame twist). I'm not 100% sure on the terminology but I understand how it works. When you're putting a lot of power to the ground the twisting of the driveshaft, which is resisted at the diff where it changes direction, can twist the axle or the whole vehicle. That would result in one wheel coming off the ground and spinning. With a limited slip, it would apply power to the wheel that remains on the ground too; if there's a lot of power you could spin that one, causing it to lose lateral traction. Since you're putting enough power down to twist all that stuff, you're not on a slippery piece of road, you've obviously got great traction. In that case, it may kick sideways a little and then the other wheel lands on the ground and you go.

However, what I've been talking about (as well as a few others here), is in slippery conditions where the spinning of both tires causes them to lose traction without much power applied at all. There's no axle hop/twist/wrap/warp involved. They're just spinning because there's little traction. Spinning tires lose their lateral traction as well as their accelerating/braking traction, which is how donuts, powerslides, and "drifting" work with RWD. When you're Just Driving Along and both tires spin (because they went on a patch of ice), they continue spinning as they get off the ice patch and the little bit of propulsion you get combined with the lack of lateral traction results in getting sideways (again, like donuts/powerslides/drifting). It's fun when you expect it, not so fun when you don't.

[dieselbenz]

Originally Posted by theholycow

However, what I've been talking about (as well as a few others here), is in slippery conditions where the spinning of both tires causes them to lose traction without much power applied at all.

But you're ignoring the fact that it takes twice as much torque to spin 2 tires (LSD) on ice or any other surface than 1 tire with an open differential. So yes, you can get to a situation where you're spinning both tires with an LSD but its far less likely to happen because you would have to be accelerating twice as hard than with an open diff. And when you get into the situation where you're spinning both rear tires you're either doing something irresponsible, driving on the wrong kind of tires for the conditions (all seasons on ICE or M/T in rain) or you don't have enough weight over the rear axle. Most unloaded pickup trucks have plenty of torque but 2/3 of the weight sits over the front tires. Throw some sand bags in the bed during the winter and reduce your rear tire pressure.

[theholycow]

Ok, I see what you're saying there. I would point out, however, that the torque required to sping both tires when you hit a patch of ice or even snow in a RWD pickup is less than the amount of torque required to maintain your current speed.

Weight and more appropriate tires can definitely help (and help the open diff as well as the LSD), but I thought this discussion was about the difference between one differential and the other, not how you can improve your safety when using either.

[dkjones96]

Originally Posted by tjts1

But you're ignoring the fact that it takes twice as much torque to spin 2 tires (LSD) on ice or any other surface than 1 tire with an open differential.

That is true in a straight line but not when cornering.

When you are cornering, once the inside tire breaks loose the outside tire is the only one keeping control. No problem if you aren't applying power to it but once you start doing that everything changes. The outside tire already has a lot of work cut out for it depending on the severity of the turn and applying power like a limited slip will do is going to send it right over the edge.

This doesn't take into account weight distribution or anything but where the power is going and what tires can do what doesn't change with any of that.