Which rear wheel get's the torque?

fritznbud

fritznbud

Senior Member
I've searched fordbarn and the internet. Without going out and burning rubber, what rear wheel gets the power? Driver side or passenger? Thanks.
 
Whichever one is turning faster. When going around a curve, the outside wheel will be getting the power. That is why once you start spinning a wheel in mud or snow, the other wheel doesn't help out, unless, of course, you have a limited slip rear end, which transfers power to the other wheel when one starts to spin too fast.

Steve
 
Time to watch a favorite gearhead film again -- My Cousin Vinny. In case you don't have a DVD player, here's the expert witness, Mona Lisa Vito, giving testimony in the murder trial.
Mona Lisa: "The car that made these two, equal-length tire marks had positraction. You can't make those marks without positraction, which was not available on the '64 Buick Skylark!
Vinny Gambini: And why not? What is positraction?
Mona Lisa Vito: It's a limited slip differential which distributes power equally to both the right and left tires. The '64 Skylark had a regular differential, which, anyone who's been stuck in the mud in Alabama knows, you step on the gas, one tire spins, the other tire does nothing.
[the jury members nod, with murmurs of "yes," "that's right," etc]
Vinny Gambini: Is that it?
Mona Lisa Vito: No, there's more! You see? When the left tire mark goes up on the curb and the right tire mark stays flat and even? Well, the '64 Skylark had a solid rear axle, so when the left tire would go up on the curb, the right tire would tilt out and ride along its edge. But that didn't happen here. The tire mark stayed flat and even. This car had an independent rear suspension. Now, in the '60's, there were only two other cars made in America that had positraction, and independent rear suspension, and enough power to make these marks. One was the Corvette, which could never be confused with the Buick Skylark. The other had the same body length, height, width, weight, wheel base, and wheel track as the '64 Skylark, and that was the 1963 Pontiac Tempest.

This said (thank you, Marisa Tomei!) Tom Endy's tretise on Differential Restoration states, "... the ring gear side ... is where the initial torque is applied." I'd trust Tom, but Mona Lisa is a lovely witness!
 
fritznbud said:
I've searched fordbarn and the internet. Without going out and burning rubber, what rear wheel gets the power? Driver side or passenger? Thanks.
Click to expand...

They both do, the one that spins is the one with the least amount of traction.
The right rear on a model A. At least on my hill climb Speedster. You can get them both to spin by jacking the weight to that side of the car. Not going to tell you how, because it is a advantage at the hill climbs.
 
Brent.
I don't have it memorized, although my youngest daughter once delivered the Mona Lisa diatribe on deer hunting (no explicatives deleted) at Thanksgiving dinner. It brought the house down! We still had my father-in-law, Colonel Nick, then and even he grinned. My kids are great!
No, I didn't post it on Ford Barn from memory. The internet has all the good stuff. You just have to ask Mr. Google!
(If you haven't seen Vinny, do yourself a favor ...)
 
Anyone here actually pass physics?

Since the driveline exerts a twisting force on a solid rear axle, the driver side axle is loaded, while the passenger side is lifted proportionally with the driveline force. A loaded wheel gets more traction than the light wheel, and assumeing the simple differential supplies equal torque to both wheels as it should, the right wheel looses traction first creating the illusion of power being applied to earth by its spinning. Sort of a believe me or your lieing eyes situation. Good Luck: Fred A
 
Thanks Fred, I was hoping you'd say that. Since i just came in from swapping my rear wheels :) My reason is that one tire has more miles on it than the other and i wanted the newer tire on my "torque" side.
 
Re: Anyone here actually pass physics?

Fred A said:
Since the driveline exerts a twisting force on a solid rear axle, the driver side axle is loaded, while the passenger side is lifted proportionally with the driveline force. A loaded wheel gets more traction than the light wheel, and assumeing the simple differential supplies equal torque to both wheels as it should, the right wheel looses traction first creating the illusion of power being applied to earth by its spinning. Sort of a believe me or your lieing eyes situation. Good Luck: Fred A
Click to expand...

BUT, the crown in the road puts more car weight on the right side. Will the driver's weight make up for it?:confused: Probably, but then you have to think about the passenger.:eek: OH, I give up.:D

George answer it. The axle torque is equal for both sides, but the tire with the least traction is the one that spins.
 
Tom and George have it right. On a hill climb for instance the torque tends to lift the right side and that tire spins. You can eliminate some of this by shimming behind the axle shafts and forcing some friction into the diff. gears. Not to tight as the housing will distort, and you want some slippage in turns.
 
Re: Anyone here actually pass physics?

Tom Wesenberg said:
...The axle torque is equal for both sides, but the tire with the least traction is the one that spins.
Click to expand...

Tom,

Can you or someone explain to me--if both wheels always get equal torque--how comes when you're stuck on mud, snow, or ice with one wheel spinning, the other doesn't seem to be doing anything to help pull you out or also start slipping and spinning? In other words, if the slower wheel is already getting torque, why are limited-slip rear ends needed?

Thanks.

Steve
 
Steve. Watch the video in my post above yours. At 5:32, they explain that when you stop one wheel, the other wheel is free to turn.

The simple answer is that one wheel is a little more stuck than the other, and therefore one wheel breaks free and one holds still.

The video really explains why one or the other wheel breaks free.
 
Jason in TX said:
Steve. Watch the video in my post above yours. At 5:32, they explain that when you stop one wheel, the other wheel is free to turn.

The simple answer is that one wheel is a little more stuck than the other, and therefore one wheel breaks free and one holds still.

The video really explains why one or the other wheel breaks free.
Click to expand...

Jason,

I did watch the video, and I thought it was excellent--thanks for posting it. But--and maybe I'm just dense--it still doesn't answer my question. I understand how one wheel can start to slip before another and, as your video shows, how the differential allows the rear wheels to go at different speeds. What I am questiong is the assertion by Tom and others that both wheels are always receiving the same torque.

If both wheels are truly always receiving the same torque, then the non-spinning wheel should be making some contribution to moving the car, but in my observation it does not. Otherwise, a limited slip rear end would make no sense; if the non-spinning wheel is already being torqued, why would it only suddenly start to act like it's receiving power when the limited-slip feature stops the spinning wheel?

I vividly recall slowly, doing a semi-controlled fishtail up snowy hills in northern Michigan as my Dodge's special-ordered limited slip rear end flipped the power back and forth between the rear wheels. Similarly, I don't understand why Positraction or similar lockups would be necessary if both wheels were always both getting equal power.

I much enjoyed that movie scene with cousin Vinnie's girlfriend describing what happens only when both wheels are truly receiving the same torque, i.e., Positraction.

Steve
 
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i was always under the impression that an open diff shifted the power to the right wheel (passenger side) . ................ steve
 
A differential doesn't shift power.

The wheels in a sense push off of each other. If one has no traction then zero power will be applied to the other wheel.

If you look at an exploded view of one it may help you understand.
 
side note if you had a car on a jack stand and both rear wheels were going 30 mph and you stopped one the other would go to 60 mph with no more speed on the drive shaft. power is follows the path of least resistance in the case of a rear diff. Buddy
 
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