Which rear wheel get's the torque?

bdotson said:
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
Click to expand...
Not true. RPM's are the same whether it is turning 1 wheel or 100 wheels the driveshaft is delivering the same RPM's at speed.
 
James Rogers said:
Not true. RPM's are the same whether it is turning 1 wheel or 100 wheels the driveshaft is delivering the same RPM's at speed.
Click to expand...


I have to disagree.

I'm fairly sure if you lock one wheel the opposite wheel will spin twice as fast.

This has to do with how the differential works not a quantity of wheels. Kind of the nature of the beast, allowing the wheels to spin at different speeds. If it didn't it wouldn't improve steering.
 
Re: Anyone here actually pass physics?

steve s said:
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
Click to expand...

Lets say there is 100 lbs of torque at the rear axle as the car is climbing a hill. Then the driver pulls over to the side of the road and tries to go again. He still has the capability of 100 lbs of torque to climb the hill, but if one wheel is now on ice and slips with only 15 lbs. of torque, then the other wheel will also still be trying to help pull, but with only 15 lbs. of torque. So, there he sits and spins, unless he has positraction, or can lock out the differential.
 
A side note, positraction/ limited slip differentials are no longer necessary. Modern cars with anti-lock brakes measure the difference between wheel speeds and selectively release/apply individual brakes. The same system can be made to apply braking to the spinning wheel, increasing torque delivered across the differential to the wheel with traction.

The same thing can be done if you are stuck with one wheel spinning in an old car. Lightly apply the brakes, more torque will cross the differential to the wheel with traction. Nothing new, this trick has been around since the advent of the differential drive axle. I got out of snow many times in the 60's by lightly pulsing the brakes with one wheel spinning.
 
Well I'm going to throw a wrench in here somewhere. Is it theoretically possible to convert a Model-A rear axle to a posi type rear axle?
 
hydroshawn said:
Thanks for some worthless comments. If I wanted those I can get them on the HAMB.
Click to expand...

It is "theoretically possible" to do almost anything. As a practical matter, I doubt there is enough room in an "A" differential to install the necessary clutches and other mechanisms needed to convert it to posi.

Gweilbaker's suggestion would convert it onto a locked differential, not a posi. Granted, a worthless comment, but funny.

Joe
 
Well I met an old timer that used to race A's. And he told me that the spider gears can be welded together but I thought they hadto be free moving.
 
hydroshawn said:
Thanks for some worthless comments. If I wanted those I can get them on the HAMB.
Click to expand...

Yes, you can get worthless comments here as well, only please notice the lack of expletives. I don't know about positraction in an A differential but there were a lot of limited slip banjoes. As mentioned the spiders can be welded to lock the axles together, squeally wheels on pavement but, good for dirt trackers. So in essense, jambing the wrench in those spiders will possible provide a non-slip differential but I doubt it will allow limited slip.
 
Re: Anyone here actually pass physics?

steve s said:
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
Click to expand...

Wiki - "The main advantage of a limited slip differential is shown by considering the case of a standard (or "open") differential where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate freely—the torque transmitted will be equal at both wheels, but will not exceed the threshold of torque needed to move the vehicle, and thus the vehicle will remain stationary."

i.e. The free wheel is applying zero torque so the other wheel will do the same.
 
hydroshawn said:
Well I met an old timer that used to race A's. And he told me that the spider gears can be welded together but I thought they hadto be free moving.
Click to expand...

Yes, if the differential can't work, then the tires will be scrubbing off rubber every time you go around a curve, or worse yet, the keys or axles might break. Plus, you will loose some steering control. That's why the rear end on my Scout has positraction, but not the front differential.
 
hydroshawn said:
Well I met an old timer that used to race A's. And he told me that the spider gears can be welded together but I thought they hadto be free moving.
Click to expand...

We used to weld spiders (poor man's posi). There were a couple of ways to do it. The easiest and fastest was to just poke a rod in the gears and weld away definately locking it. The more civilized method was to remove the spiders and weld between the gear teeth in one or two spots. That would allow some gear movement, good for a corner turn but not a U turn.
 
Tom Wesenberg said:
Plus, you will loose some steering control. That's why the rear end on my Scout has positraction, but not the front differential.
Click to expand...

True, that's why our dirt track car had welded spiders and NO front brakes. It wouldn't stop worth a damn :eek:, but it sure could be aimed. :D
 
Last winter I drove my car in the snow many times and every time my right rear wheel was the drive wheel when going completely straight, no turns..... I actually was playing around and making the old Guy skid to just get the feel for it in a parking lot that was empty and at all times the right rear wheel was the main drive. Maybe something is wrong with my car? But all seems to work well and I do not have any drive train problems that are noticeable.....
 
One factor is the pinion gear trying to climb the ring gear is pushing down on the ring gear. This pushes down on the wheel on the ring gear side. This causes slightly more loading therefore more traction on the ring gear side. All other things like road surface, weight and tire being equal the right side with less pressure will spin first. Consider what would happen if the rear end were floating free. The engine would tend to spin the entire rear end rather than turn the axles.
 
inex01 said:
Last winter I drove my car in the snow many times and every time my right rear wheel was the drive wheel when going completely straight, no turns..... I actually was playing around and making the old Guy skid to just get the feel for it in a parking lot that was empty and at all times the right rear wheel was the main drive. Maybe something is wrong with my car? But all seems to work well and I do not have any drive train problems that are noticeable.....
Click to expand...


This is usually because there is more weight on the left side of the vehicle (driver).

Another note is, at least to my knowledge, Positraction is a Pontiac (I think) name for limited slip. They are the same thing. Don't kill me if I'm wrong, it happens.
 
You must log in or register to reply here.
Back
Top