I don't think the engine RPMs would sixtiple (multiply 6 fold) as fast as the transfercase could engage. I'd bet on the transmission or torque converter exploding first.

 

Whether you are in 2 or 4 spinning is a problem.

That is why I generally leave it in 2 for most occations. Icy roads, offroad whatever it is if I can navigate it in 2wd I like to have the 4wd for standby.

 

It won't go into 4Lo when you're moving. I flipped it too far one day and it made all kinds in weird sounds and would not go in till I came to a complete stop and shifted into neutral...

 

Yes, 4lo will not engage unless both the transmission is in neutral and the brake pedal is pushed. Before I knew how to properly engage the 4lo feature, I switched into it while driving slow but nothing happened. You can actually hear the transfer case dropping into 4lo when done properly.

And yes, 6637 is correct that the manual that VASherrif pasted from was wrong, in that four wheel drive really means two wheel drive unless specially equipped with a locker of some sort.

 

Ford set it up like that so nobody will damage any of the high ratio parts.

 

Nope. Very common myth, but not correct.

A hypoid differential's purpose is to provide the exact same torque to both wheels on an axle while allowing for a differential in speed. The speed differential happens whenever all four wheels are going perfectly straight, as whenever the vehicle is turning some wheels have to spin faster than others.

The problem occurs whenever an "open" differential axle encounters a situation when one wheel gets a great deal less traction than the other, the wheel that gets the traction is LIMITED to the amount of torque the slipping wheel can take. This is why the slipping wheel always seems to spin up, because it is limited to the traction available and once the wheel breaks free, the other wheel is limited in this respect as well.

Remember, both wheels HAVE to get the exact same torque with this type of diff. There is no "one wheel drive", and likewise four-wheel-drive really does mean 4 wheels. They may not all get the same traction, but they are all being provided torque. Just no more torque than the opposite wheel is, that's all.

 

That's right, when you are in 4 wheel drive on pavement all 4 wheels are pulling the same. If 1 wheel loses a degree of traction the opposite wheel is still pulling . It ranges from 1 to 100%. You could have 30% pull on your right wheel while the left one has 70%. When 4 wheeling on a steep back road all 4 are pulling and they can shift back and forth in torque as you go. When I used to dragrace cars I welded up my spider gears to lock a rear end (poor mans positraction) and one side broke loose so all the power went to 1 wheel. The car pulled to the right when I hit the gas and I could pass someone on the highway while smoking 1 tire the whole way since all the power went to 1 wheel.

 

Kind of a cool example, EXv10! As you just demonstrated, if there was true one-wheel-drive, you'd have a very strong pulling in your steering wheel all the time.

This can't happen with an open differential, regardless of whether it's on pavement or ice. Say, for example, one wheel is on ice and the other is on pavement, each wheel would be pushing the truck with the exact same force, as the one that grips would be pushing only as hard as the one that doesn't.

Never heard of someone welding the spiders on a car that'd ever see public roads...I bet it handled kind of scary, even after the weld broke and you had your one-wheel-drive car...

 

Well, when you are just a kid with a souped up 55 Chevy and no money anything goes. I was first intrigued with the differential when I was watching a tractor stuck in the mud at school when I was about 12. One wheel was just spinning occasionaly and it baffled me for days. I later became a mechanic.

 

No I think the transfer case will self destruct !!

 

With regards to 4 - Low/High on paved roads. I have had to use 4-low to tug my trailer up a steep driveway. Also asked mechanics prior to trying and they had no objection - said it'd take some load off the trans especially in reverse. Is this wrong? Certainly "feels" much easier...

 

Will definitely take load off of the transmission, as there's a 2.72:1 reduction gear when you're using 4lo. The biggest problem with using 4WD on pavement is when you go to turn the wheels. If the wheels are straight, or very close to straight for a short amount of time, you won't likely have any significant binding in the driveline.

Not sure about you Excursion folk, but can you lock out your front hubs manually? If you were to shift to 4LO and lock your hubs out, you'd instead be in 2LO, which would take the strain off of your tranny without fear of damaging your driveline.

 

I think it is a great idea if the road doesn't have any sharp turns.

 

What is the purpose of putting a locker in your diff if a normal diff has the ability to power both wheels ... I'm confused

 

It only powers all 4 wheels until one breaks loose. One won't break loose with a locker. Even when 1 breaks loose there is still power to the opposite one but it depends on how much friction is on the spinning one. That is why I said it varies from 1 to 100%. .....100% is always going to both wheels added together but the power is going more to the spinning wheel even though it is going to rotational force and heat. Let's say one wheel is on ice and the other is on pavement; the one on ice might have 92% of the power going to it (even though it is being wasted) while the opposite one will have 8% going to it so it seems like the static wheel is doing nothing while it is actually pulling by 8%.