Differential binding with wheels turned

[hodge5]

Regardless of what types of joints are in the knuckles, they will have their limit to how tight they can be angled before they bind. I would run the truck with the wheels off of the ground, and slowly turn the steering one direction- see how far you can steer before the binding starts. Then, turn the other direction, slowly, isolating when it starts. Of course, this may also rule out the steering joints as the culprit.
If you have changed the angle of the pinion, the axle could be rotating some under throttle, and increasing the pinion angle, to the point that the u-joint is binding.

[emilsolbat]

In my experience, the shaking/jumping is NOT because of the universal joint is binding. It is because of the difference in input- and output rotational velocity in the joint, when it's at an angle.

The input shaft rotates at a constant speed, but the output (wheel) speed fluctuates. The sudden changes in output velocity, along with the mass of wheels and tyres, causes the entire axle to jump and shake. If you test it without the wheels, it won't behave like this.

This video shows the physics behind it:

[hodge5]

Originally Posted by emilsolbat

In my experience, the shaking/jumping is NOT because of the universal joint is binding. It is because of the difference in input- and output rotational velocity in the joint, when it's at an angle.

The input shaft rotates at a constant speed, but the output (wheel) speed fluctuates. The sudden changes in output velocity, along with the mass of wheels and tyres, causes the entire axle to jump and shake. If you test it without the wheels, it won't behave like this.

This video shows the physics behind it:

Then, why don't they all do it?
I do agree with the physics of the universal joint. But, the knuckle can turn to a point that the joint starts to bind- there is a limit to the angle.
Also, there are different types of joint used. And, not all axles operate with the jerking and binding. It is important to distinguish between fluctuating speed of the output shaft, versus shaking and binding.

[emilsolbat]

Originally Posted by hodge5

Then, why don't they all do it?

I don't think I've seen a truck with locked diff and regular universal joints, with decent steering angle that doesn't have this problem. I may be wrong, but I think this is an inherent flaw with the standard U-joint.

If you have an open diff, i believe the forces cancel out each other to some degree.

If you have very light weight wheels, the shaking may not be as prominent.

Also, I don't think it's something most people notices when driving. With the weight of the truck on top, at an uneaven surface, the axle shaking is hard to see.

[emilsolbat]

Originally Posted by hodge5

Then, why don't they all do it?
I do agree with the physics of the universal joint. But, the knuckle can turn to a point that the joint starts to bind- there is a limit to the angle.
Also, there are different types of joint used. And, not all axles operate with the jerking and binding. It is important to distinguish between fluctuating speed of the output shaft, versus shaking and binding.

Of course, I agree that binding can occure. And with that, the shaking becomes even worse.

My trucks also have this problem, but it all spins smooth through the whole rotation, so no binding.

[WhatsInYourHead]

my truck had similar axle hop and once i ditched the crappy axial driveshafts i found out it ended up being a warped spur gear from the box on my rtr. i swaped it out and it made a big difference. i guess the vibration in the trans continued down the drivetrain.