Rear Locker in 2 and 4 high

No, I'm not saying that at all. That becomes a totally different scenario and even worse for scrub. With everything locked in 4H now each individual wheel is forced to rotate with equal speed. Now the bind is absolute max for a given turn because the total bind comes between the single wheel traveling the longest path and the single wheel traveling the shortest path.

In 4H with the diffs open the bind is the difference in the sum of the path of the front wheels and the sum of the path of the rear wheels. This will be less than the difference in the single longest-path wheel and single shortest-path wheel so therefore less bind with the diffs open in 4H than with the diffs locked in 4H.

 

yes, never had an issue. The arb lights up when engaged.

 

It does light up. The button lights up when engaged....

 

In 4HI ONE of the rears and ONE of the fronts HAS to turn at the same speed. You can mix and match which ones but two are locked together with an open diff front and rear. With 4x4 engaged and one locker Engaged 3 tires have to turn at the same speed.

 

That’s how I always understood it but ShimStack says “The sum of the speeds of the front wheels MUST match the sum of the speeds of the rear wheels.” So isn’t he saying all the wheels have to spin at the same speed? I thought only one front and one rear did with an open diff like your saying. I know I can run 4h on the pavement and corner with some resistance and pull when cornering but when I have my front locked in the same scenario it’s almost impossible.

 

I’ve never used the ARB locker switches. Just aftermarket ones. So the ARB switches have a secondary light that lights up when it’s locked?

 

Yes

 

Let's get some fundamentals straight on how an open diff works:

1) The 2 output torques are equal
2) The 2 output speeds must average out to the speed of the differential carrier

So, to get differential speed outputs, the fast wheel must be turning faster than the carrier by the same amount the slower wheel is turning slower than the carrier. When one wheel has zero velocity and the other is spinning it is actually spinning 2x faster than if both wheels were spinning equal speeds with the given input speed or 2x the speed of the carrier.

Example scenario. 4H, rear locked. The only scenario where 3 wheels have the same speeds is when all 4 wheels have the same speeds. The rear wheel speeds will always match each other and if there's no differentiation going on at the front then those front speeds will match each other and match the rear wheel speeds. As soon as one front wheel begins to over run the opposing front wheel then you have 1 front faster than the two rears and 1 front slower than the two rears. The amount one is faster than the rear wheels is the same amount one is slower than the rear wheels. Again, the sum of the 2 front wheel speeds will match the sum of the 2 rear wheel speeds. This fact is forced by the transfer case being locked and driving both axle inputs at equal speeds.

 

They have an independent top light. You can wire that light however you like, but typically it’s wire to where when the switch is in the on position it lights the top light up. Has nothing to do with weather or not there is power supplied to the locker.

 

No, when the switch is in the "ON" position its lights the switch but it has no logic on what position the differential/locker is in.

 

I’m floating the river in this 95 degree heat and think I’ve had one too many to drink. My brain is being overloaded with too much info right now. Will revisit this all tomorrow. Thanks for all the input everyone but time for another one and some more eye candy.

 

Okay I’m back. Can you answer this for me?

When in 2wd I can gas it and spin one of the wheels faster than the other one. Real easy to do in the ice and the traction control will kick in to limit the free spinning wheel. Now when you put it in 4h it locks the center up so equal force is being applied front and rear but does nothing to the rear end so from side to side they can still spin at different speeds even though equal force is being applied to all wheels. And just like in 2wd, when I’m in 4h I can gas it especially on loose surfaces and get sideways because from side to side the wheels aren’t spinning at the same rate and once again traction control will kick in to apply brakes to the faster spinning wheels.

So you can have the wheels spin at different speeds from side to side even in 4h. Equal force might be applied to all corners but with the open diff you can spin them at different rates.

Now am I just drunk or is this correct?

 

If you have one tire in the front off the ground, and one tire in the rear off the ground, in 4HI, and hit the gas, they will spin freely at the same speed. The other two tires on the ground won’t do anything.

One wheel in the front has to spin at basically the same speed as a wheel in the back. The other two wheels can do whatever they want. Spin faster, or not at all.

 

That’s what I thought and makes sense. So from side to side they can spin at different rates. Tell that to ShimStack. He says otherwise but he doesn’t make sense. It does make sense that equal force might be applied but that doesn’t equate to equal speed.
That’s why in 4h when cornering the outside wheels can rotate at a different speed than the inner wheels.

 

Turning a corner in 4hi, there are 4 wheels all travelling a different distance, and wanting to spin at 4 different speeds.

But they can only travel 3 speeds as one in the front and one in the back are locked together and turning in unison. One of those tires will scrub.

 

In 4Hi with the diff locked, only 2 speeds are possible. With two lockers only 1 speed is possible.

 

I'll try.

Yep

No. This is a huge problem with the intuitive understanding of a locked differential and in this case a "locked" center differential. We have to get terms straight. It's not force, it's torque we're interested in. And, NO, equal torque is NOT being applied front to rear. Equal speed is and only equal speed. I've already mentioned earlier the torque bias (torque applied) can be biased from 0 to 100% front to rear with a locked center. I understand this is difficult for most to grasp, but it's true.

Again, equal torque (you used force) is not being applied to all wheels. Equal torque is applied to each wheel on each axle because that is a property of an open diff. So the torque at the LR = torque at the RR, torque at the LF = torque at the RF, but torque at the rear wheels does NOT equal torque at the front wheels. And again, side to side can spin at different speeds but only within the parameters an open diff may operate. This parameter is that it must output speeds in any ratio such that the average of both outputs equals the carrier speed. It can't output any speed to any wheel, it can only output speeds that satisfy this parameter. Period. You're piling on lots of physics at once and making this hard to explain and understand.

You don't break loose because wheels aren't spinning at the same rate, you break loose because the tractive limit has been breached.

You can have speeds different side to side in 4H, yes. BUT, they still must satisfy the physical condition that the average speed of the L and R must equal the carrier speed. The issue is the carrier speed is fixed and cannot be different between the front and rear. So because the inputs at the F and R axles must spin the same speeds the ideal total speeds of the L and R wheels can't quite be satisfied by the open diff, there's a limit of which it can do and it's bounded by the requirement that both the input speeds at the front and rear axles must match.

You're still drunk.

I'm only repeating myself at this point. All the physics that cover your questions I've stated previously in this thread. My suggestion if you want to keep going is work on bare bones basic examples to pick up each concept one at a time before looking at broad examples that require combinations of concepts.

 

3 speeds are possible. See post #70.

That's correct.

 

I said force which should be obvious to be torque. Could also say horsepower maybe? Force implies both torque and horsepower for me. Sorry if it’s not technically correct.

You previously said “In 4H your axle diffs may be open but the transfer case is locked and must output equal speeds front to rear.” So that is why I said equal force is applied to both ends as I was going off what you said but I guess I misinterpreted speed for torque. My bad.

“Equal torque is applied to each wheel on each axle because that is a property of an open diff.” I guess I also misinterpreted this as you saying equal torque is applied to the front and rear. My bad again.

So basically equal torque is applied to each wheel in a open diff but not equal speed? But in a locked diff equal speed is also applied? If that is the case then how can being in 4H be worse than driving with a locked diff when cornering? This is where this conversation started from. Once again I can drive my truck in 4H on pavement and go around corners without too much effort but if I lock my front diff up it’s almost impossible to make a turn. How is that being easier on the truck than being in just 4H? You said in 4H speeds can vary from side to side. I know this is not possible with a locked diff. Not sure how this can be easier on the truck. I guess that is the one thing I still don’t understand in all this. Try driving a truck with the front diff locked around a corner and then try it in just 4H them you’ll understand why I think 4H is easier on the drivetrain than driving with a locked diff on the pavement.

“You're still drunk.”

No, down to a light buzz.

 

There is play in the differentials but no play in the transfer case.

When you bind up in 4x4 (front to rear axles trying to move at the same speed but can’t) you stress the transfer case. When you bind up on a single axle that has a locked diff, you stress the diff. The diff has play in it by design.

Since the transfer case splits force 50/50 front to rear, the axles will be moving at relatively similar speeds when you’re cornering in 4x4. When you’re cornering with the locked front diff, the difference in wheel speed is significantly different left to right. This is why you can get away with driving in 4x4 for a bit before you notice the bind but you’ll notice it right away with the locked diff.

Both kinds of bind are bad. One has a smaller chance of actually breaking something.