Rear Axle Question

[WhoMe08721]

Hey Guys,

Today I was working on my buddy's M35a2 Rear axles and I notice when I spin one tire the other spin in the opposite direction and I cant hold one side when you spin the other side. I thought the axle where open diff, There for I thought you could hold one tire on one side when some one spin the other side. Is this correct??

 

[Fatalid]

If the driveline is not engaged and free to spin, you can hold one wheel still while turning the other wheel. But if you were driveline is not moving, spinning one wheel will result in the opposite wheel spinning the opposite direction.

 

[WhoMe08721]

The Hole Rear of the truck is on jack stand and off the ground. The truck is in neutral so the driveline should be free to spin. I should be able to hold one wheel, while turning the other wheel. But I can't, when I spin one wheel the opposite wheel spinning in the opposite direction and can't hold it.

 

[Fatalid]

Is the parking brake on?
Keep in mind you’re also trying to overcome the resistance of moving the entire other rear axle differential and tires.
Can you turn the driveshaft by hand?

 

[dmetalmiki]

HA! But you see, You ain't superman.
If You had ALL the rear wheel jacked up, and chose to turn any one of the rear axle wheels, you are trying to rotate a horrific amount of mass.
The differential in any one axle is just that, 'A differential', DIVIDING the force (Turning input) EQUALLY, (In a straight (Driven) line, BUT, When you turn (simulating a corner) what ever the OUTSIDE wheel rotation is, the INSIDE wheel turns exactly less in proportion.
So, (Phew). YOU turn one wheel (ONE side jacked up) at 2 rpm, the other wheel will respond by rotating 2 rpm backwards.
IF you place the wheels on the floor, you can (!?) turn the prop shaft and BOTH wheels will rotate at the same output rotation. (No snow etc).
However if there is ice on the floor the wheel with grip will be stationary whilst the opposite wheel now spins on the 'ice' at TWICE the rotation (Input) Speed. (Little resistance).
IF clear of the ground it is not going to fight any drag at all, So the resultant torque will cause it to rotate backwards.
IF it was HELD LOCKED then the driving force would go equally to both wheels (If on the same terrain). And be torqued round equally in the same direction.
Come to a corner (And if you like) The torque is divided equally to allow the outside wheel to turn faster than the inside wheel, round the given radius of the corner. Thus avoiding scuff and wear. (One wheel effectively 'travels' further than the other).
6x6 is like LOCKED (Forward just by the mass etc) when jacked up.
So, You twiddle one way and the other wheel with no resistance will oblige by going opposite in direction. (Phew!).
And Even more 'Phew'! If you want me to tell you what's going on with 6x6 and or 8x8.

 

[TGP (IL)]

It is a open Diff if one wheel goes in opposite direction.
Most are open Diff's.

Your trying to overcome a large set of spider gears.
Pretty hard to do by hand turning a wheel.
Tom

 

[rustystud]

The Hole Rear of the truck is on jack stand and off the ground. The truck is in neutral so the driveline should be free to spin. I should be able to hold one wheel, while turning the other wheel. But I can't, when I spin one wheel the opposite wheel spinning in the opposite direction and can't hold it.

What you fail to understand is the "Rockwell" differential is a "double reduction differential. One end has a "spur" type of input gear, just like most winches do. They do not turn easily from the other end (the big gear) that in turn goes to the input gear, so your trying to turn two types of gear sets. That is why the driveline does not turn. It acts like it is held. Therefore the wheel spins the opposite way.
Here's a picture showing what I mean.

 

[Floridianson]

What about the transfer case was that in neutral?