Wetspirit, it doesn't matter if the torque is going to the ground or not. That is only serving to confuse you as to where the power goes. You are correct in that in a straight line with no wheel slip between the tire and ground both tires are receiving equal power. I used the example of a tire in the air because it shows where the force goes when you give the axle more power. From a stand still both tire are motionless. You give the axle power through the transmission and what happens to the tire in the air? It begins to accelerate and spin. That is where the power is going on the open differential.

 

lockers are the only way to go offroad. onroad they are a bit scary, depending on the wheelbase. my 72 bronco will scare the bajezus out of you if the front is locked in..

 

When I say torque I'm talking about the force being delivered to the ground, the forward thrust being delivered by the tire. It is always equal with an open diff. If one wheel is off the ground neither one is delivering power to the ground, if one wheel has a little traction, like in snow, they are both applying equal forward force to the ground, even if one wheel is spinning. Your example of a wheel off the ground absorbing power is only true to a certain extent. Yes it is spinning but it is not applying power to the ground and neither is the one on the ground. They are applying equal driving force. Force that is limited by the tire with the least traction, but ALWAYS equal. The tire spinning in the air is only absorbing enough power to spin it up and the tire on the ground applies a forward force equal to the energy required to spin up the other tire and that's all. It might be slightly more accurate to say that both axles in a given differential housing are equally resisting the torque from the differential. If you could apply the brake on the spinning wheel only, the wheel on the ground would apply a forward force equal to the resistance of the brake on the spinning wheel. Again, always equal. A straight line has no affect on this with the open Diff. Straight, curved, whatever. Always equal torque but almost never equal speed. While the spool has always equal speed but almost never equal torque (there really is, practically speaking, no such thing as a straight line while driving).
I wish I could think of a better way to explain this wonderful machine, but the best thing is to go play with one. You can jack up your truck and try a few experiments or find one at the junk yard with the cover off to play with. You'll see what I mean.

Wetspirit

 

How would you explain torque steer in a FWD car then? If what you are saying is true, both the motionless tire and the moving tire receive 1/2 of the input torque. It is correct to state the differental split torque but not always equally. I would be more inclined to belive you if you signed your name with BSME, MSME...etc

 

jkitterman,

Torque steer on FWD cars is a combination of many things. Unequal length half shafts, tire offset, scrub radius, tires and road conditions.

With unequal length half shafts, you will also have unequal weight of shafts. The higher weighted shaft will require more of the equally divided torque itself to get moving or accelerate than the lighter one, leaving less for the tire.

With scrub radius, the distance between the center of the contact patch of the tire and the steering axis, is ideal equal on both sides, but often not perfect. When torque is applied the tire is trying to pull itself around the steering axis, causing the car to try and steer itself. If the scrub radius is not equal on both sides than you get torque steer. Also, if you have a different offset than factory, your srub radius could be even worse.

Road conditions also cause a problem. If you are driving on a perfectly smooth road (yeah right) then traction would be equal on both tires, but that is rarely the case.

Hope this helps.

Gord.
BSME