Limitations of Limited Slip

[MastuhWaffles]

Recently after the rain I went out in the mud to test out my limited slip. Both tires would spin on relatively flat ground, but when I got to a bump and put on side of the axle in the air, the other side refused to spin and give me traction. Is this just because it needs to be rebuilt, or does limited slip have its limitations?

 

[Captain Ledd]

Limited slip's limitations.

What you're expecting is a locker, which has teeth/splines that engage the carrier itself so that both axle shafts spin the same speed as the carrier no matter what kind of traction the wheels may (or may not) have. This is the only way to get a wheel to spin with the other in the air.

Clutch type limited slips work by the natural way gear teeth want to force themselves apart from each other. This compresses the clutches against the special plates that are keyed to the carrier (those little tab parts you'll see in there). This kinda helps transmit some extra traction to the slipping tire, but only if the other tire has traction because, "bias ratio". All limited slips have it, it's a factor of how much traction the slipping wheel has. Say a L/S diff has a 3.5 bias ratio (common Torsen ratio), that means the carrier can transfer 3.5X the traction generated by the slipping wheel to the wheel that still has good traction. Obviously if your wheel is in the air, 0 X 3.5 = 0. Also very little traction, still means very little power transfer. A Torsen L/S does much the same thing but with gears, but the principle works the same.

 

[MastuhWaffles]

Limited slip's limitations.

What you're expecting is a locker, which has teeth/splines that engage the carrier itself so that both axle shafts spin the same speed as the carrier no matter what kind of traction the wheels may (or may not) have. This is the only way to get a wheel to spin with the other in the air.

Clutch type limited slips work by the natural way gear teeth want to force themselves apart from each other. This compresses the clutches against the special plates that are keyed to the carrier (those little tab parts you'll see in there). This kinda helps transmit some extra traction to the slipping tire, but only if the other tire has traction because, "bias ratio". All limited slips have it, it's a factor of how much traction the slipping wheel has. Say a L/S diff has a 3.5 bias ratio (common Torsen ratio), that means the carrier can transfer 3.5X the traction generated by the slipping wheel to the wheel that still has good traction. Obviously if your wheel is in the air, 0 X 3.5 = 0. Also very little traction, still means very little power transfer. A Torsen L/S does much the same thing but with gears, but the principle works the same.

I see now, on flat ground with both wheels touching it worked fine, but when that one tire was sitting there spinning on the bump the other one would not turn. I though it was pretty much if one wheel slipped the other wheel would get power and start spinning but apparently not. It's much better than an open differential I will say.

 

[kunar]

assuming its got some miles on it, a rebuild would definitely help. plus, if you do rebuild it, you can re-stack the clutches and steels in a way that makes more surface area. other than that, putting on your parking brake enough to put some drag on that spinning tire should help transfer some power to the other side.

 

[35Remmy]

Kunar, very interesting. Never heard or thought about applying the parking brake some to engage the limited slip.

 

[adsm08]

The parking brake trick is what you really need to remember. It puts drag evenly on both sides so if you have one side with 0 you can increase that without putting any more on the other side. It can also help you get unstuck from snow or ice with an open rear.

 

[MastuhWaffles]

The parking brake trick is what you really need to remember. It puts drag evenly on both sides so if you have one side with 0 you can increase that without putting any more on the other side. It can also help you get unstuck from snow or ice with an open rear.

Since it rained again I think I will go give it a try.

 

[desertruck]

Put the e brake on one click...it will put enough resistance on the tire in the air to make the tire on the ground spin

 

[85_Ranger4x4]

L/S is intended more for "tires on the ground" situations. Mud, snow, ice etc....

 

[ab_slack]

Yes the brake trick, as Adsm08 says even with an open diff.

Make the tires work against the brakes. Any rotation you get will help move the truck.