4wd drive vs 2wd w/locker

John W

Observer
Yes, my rear axle is a Sterling 10.25 or 10.5 whatever they put in the '99 F-250's.
Appreciate the info on options and stuff.

I'm not ready to do a locker yet, got a list of other things ahead of that. Mostly building it into a minimalist offroad camping van, easily reconverted for cargo.

I have no specific terrain/destinations in mind, most of the good stuff it seems is on the opposite side of the country.

Some of that terrain looks deceptively safe, but turns out being very treacherous in the wrong conditions or with the wrong equipment.

So, although I could do plenty of travel with a simple 4x4, that's why I'm weighing things like lockers, hi-lift jacks, winches, anchors, etc.
 

jbob

Observer
I did. The transfer case is front rear. The only way anything is transferred side to side is a limited slip. A locker locks both sides together and therefore doesn't transfer power from side to side.

Thought I'd jump in too. Technically speaking, this is not correct. I think folks are confusing wheel speed with power.

An open differential on the axle equalizes the torque sent to both sides. When one side of the differential has zero traction (e.g., with a wheel in the air), the torque going to that side is negligible. The open diff in turn sends zero (or negligible) torque to the opposite side, which may or may not have traction. A locked differential, on the other hand, does indeed transfer torque (thus power as well) from side to side, since it's not trying to equalize the torque going to each wheel. The side with the most traction at any given moment will experience the highest torque.

Regardless of what kind of differential you have, if a wheel is in the air, it gets essentially zero torque (thus power as well), other than that required to overcome the mass moment of inertia. Draw a free body diagram. Same principles apply to a center diff.

Perhaps it's just semantics, but I just wanted to point that out (sorry). Great discussion.
 

toylandcruiser

Expedition Leader
Thought I'd jump in too. Technically speaking, this is not correct. I think folks are confusing wheel speed with power.

An open differential on the axle equalizes the torque sent to both sides. When one side of the differential has zero traction (e.g., with a wheel in the air), the torque going to that side is negligible. The open diff in turn sends zero (or negligible) torque to the opposite side, which may or may not have traction. A locked differential, on the other hand, does indeed transfer torque (thus power as well) from side to side, since it's not trying to equalize the torque going to each wheel. The side with the most traction at any given moment will experience the highest torque.

Regardless of what kind of differential you have, if a wheel is in the air, it gets essentially zero torque (thus power as well), other than that required to overcome the mass moment of inertia. Draw a free body diagram. Same principles apply to a center diff.

Perhaps it's just semantics, but I just wanted to point that out (sorry). Great discussion.

Wrong


Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.
Benjamin Franklin
 

toylandcruiser

Expedition Leader
A locker acts like a spool until you turn. Then it unlocks. When youre done with the turn it locks back up just like a spool.
An open applies power to both in a straight line. Once one tire has less traction. The power goes that route

http://youtu.be/gIGvhvOhLHU



Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.
Benjamin Franklin
 
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jbob

Observer
A locker acts like a spool until you turn. Then it unlocks. Whe yore done with the turn it locks back up just like a spool.

That's correct for automatic lockers. I believe most of them (like a Detroit locker) will allow one wheel to freewheel faster than the other, e.g., the outside wheel while turning on pavement. Selectable lockers (like ARBs or the electric lockers on my rig) act like an open diff when not selected and like a spool when they are.

An open applies power to both in a straight line. Once one tire has less traction. The power goes that route

I understand what you're saying, and it's a good way to visualize the limitations of open differentials. But trust me that an open differential sends power equally to both sides...it's just physics.
 

T.Low

Expedition Leader
My inside tire does a lot of digging.


WinthroptoOroville002k.jpg
 
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toylandcruiser

Expedition Leader
That's correct for automatic lockers. I believe most of them (like a Detroit locker) will allow one wheel to freewheel faster than the other, e.g., the outside wheel while turning on pavement. Selectable lockers (like ARBs or the electric lockers on my rig) act like an open diff when not selected and like a spool when they are.



I understand what you're saying, and it's a good way to visualize the limitations of open differentials. But trust me that an open differential sends power equally to both sides...it's just physics.

You're right an arb or electronic lockers are spools and don't allow differential between sides. In an open rear end. Put one tire on a jack and the other on the ground. Now try to drive away. Its not going anywhere no matter how far you mash the gas pedal. It's doing what it's designed for.


Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.
Benjamin Franklin
 

jbob

Observer
You're right an arb or electronic lockers are spools and don't allow differential between sides. In an open rear end. Put one tire on a jack and the other on the ground. Now try to drive away. Its not going anywhere no matter how far you mash the gas pedal. It's doing what it's designed for.

I agree 100%. Also, if I read your previous posts correctly, your point is that a 4x4 with open differentials front and rear is going to be limited in some situations, e.g., when opposite corners are loaded (and the unloaded wheels just spin). If your center diff is open as well, you could have three wheels on the trail, but the one wheel in the air is going to spin, and you're not going anywhere.
 

toylandcruiser

Expedition Leader
I agree 100%. Also, if I read your previous posts correctly, your point is that a 4x4 with open differentials front and rear is going to be limited in some situations, e.g., when opposite corners are loaded (and the unloaded wheels just spin). If your center diff is open as well, you could have three wheels on the trail, but the one wheel in the air is going to spin, and you're not going anywhere.

Absolutely


Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.
Benjamin Franklin
 

IdaSHO

IDACAMPER
Sweet pal. You're not right.

PROVE IT.

My statement is 100% correct.

Originally posted:

Traditional full size transfer cases when engaged in 4x4 send equal power to front and rear. Even with open diffs, you will never have just one tire spinning, you will have TWO.

As stated, with a transfer case sending equal power to front and rear, and open diffs on both ends, wheel spin will NEVER be limited to just one tire. Once you get to wheel spin with an open diff front and rear you will have wheel spin from TWO tires. One in the front, and one in the rear. Furthermore, the spinning tires will traditionally be on opposite side, as in right front, and left rear, simply due to weight distribution and COG.


Now prove it wrong.
 

toylandcruiser

Expedition Leader
PROVE IT.

My statement is 100% correct.

Originally posted:



As stated, with a transfer case sending equal power to front and rear, and open diffs on both ends, wheel spin will NEVER be limited to just one tire. Once you get to wheel spin with an open diff front and rear you will have wheel spin from TWO tires. One in the front, and one in the rear. Furthermore, the spinning tires will traditionally be on opposite side, as in right front, and left rear, simply due to weight distribution and COG.


Now prove it wrong.

Like I said. Jack up one tire off the ground. Put it in gear and drive. It's not going anywhere.




Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.
Benjamin Franklin
 

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