Two questions I always forgot to ask that no one talks about

Depends on the truck. Some do, others don't.

 

Regardless of what the wall is made of, if you think you might bump it, then you've got no business getting close to it IMHO. The bumpers should prevent any damage to the wall or trailer if tapped lightly. But that's only true if the bumpers are what touches the wall first. If you're not backing into a dock, then you really can't be sure what's going to touch first. If there is a grade or hill or bump in front of the wall, the top of your trailer might touch before the bumper does. If there is anything on the wall like a light or utility box that you didn't notice, chances are you will hit that before the bumpers touch.

For those reasons and more, my rule is don't ever hit the wall. I'm not proud so I get close with the mirror and then I get out and look. Then I get closer and I get out and look again. When I get within a foot or so of where I want to be, I'll usually use reference points on the ground below my step. If I've got to move about 6" I look straight down and find a mark on the ground and then I creep back watching the mark in relation to the step. I'm not sure I'd recommend other people do this, but its a method that works very well for me when I have to back close to something without touching it.

 

Behind the U-joint on the front of the front differential is the power divider, through which runs a shaft to the U-joint on the back of the front differential. With the power divider disengaged, the power is transmitted straight through the free wheeling front differential driving only the rear differential. When the power divider is engaged it locks in the front differential and the power is distributed between the two. It is conceptually the same as the drive line in a fwd pick up. It does absolutely no mechanic harm to run down the road with the power divider engaged. The harm comes when the power divider is engaged and wheels are spinning. DO NOT spin the wheels with the power divider engaged! One wheel spinning and one not on each differential , causes the planetary gears inside the power divider to spin twice as fast as when all wheels are turning together. This will cause excessive heat and eventually the power divider will eat it self up. The next time you see some yahoo trying to spin him/herself out of being stuck go put you hand on the power divider and see if I'm not lying.
The power divider does not lock the wheels it joins both differentials together. The idea is that, with the power divider engaged, if one of the wheels on either differential, loses traction, most likely the wheels on the other differential will have better traction due to uneven road surfaces, slick/icy patches, etc. and the differential with traction will pull the other to a point on the surface where there is better traction. If both differentials have wheels that are spinning you are going nowhere. Break out the chains or call a tow truck. Don't try to burn through the ice by spinning the wheels, you are tearing up the power divider. The same principle applies, as your going down the road. With the power divider engaged, in the event that a wheel on one differentials slips, the differential with traction will pull the other to a point on the surface where there is better traction. The power divider can be engaged with the truck in motion as long as there are no wheels spinning. As was said above, engage the power divider only with no power load on the drivetrain by first letting off the throttle.


About the walls, If they are not your's stay off them.

 

This is pretty much the method that I used, except I would heel to toe measure from the end of the trail to two or three feet before whatever it was I didn't want to hit and transfer that measurement to the point on the ground under my step, marking with sticks or rocks or a flashlight.

 

Another misconception. With the power divider unlocked, both front and rear diffs apply equal power to all four drive wheels until one wheel position breaks traction, then all power is directed to that spinning wheel which is now turning at twice normal wheel speed through the differential gearing. When one wheel on an axle has lost traction and is spinning, wheel speed doubles on the spinning wheel. The only way to correct this to make the other three drive position wheels pull (without locking the power divider) is to provide traction to the spinning wheel (lime, sand) or apply the brake on the spinning wheel and the other three wheels will pull.
This goes right along with the simple statement of: ALL WHEELS PULL UNTIL ONE WHEEL BREAKS TRACTION.

When you can't move and you have one wheel spinning and the other three wheels won't pull, fix the spinning wheel (provide traction) and the other three wheels will regain power and pull.

Now, when you lock in the power divider, this changes the simple statement, but only slightly:
WITH THE POWER DIVIDER LOCKED, ALL WHEELS PULL UNTIL TWO WHEELS BREAK TRACTION.

 

I beg to differ. The tires on the rear differential will always wear faster because the rear differential is constantly driven and if a wheel spins with the power divider disengaged it will always be one of the two wheels on the rear differential. Unique to International, when the parking brake is engaged the power divider is automatically engaged locking both differentials together thus providing parking brakes on both differential s with parking break cans on only one differential .The best explanation, that I have found, of how a differential works is here: http://m.youtube.com/watch?v=yYAw79386WI

 

The flow of torque through a differential starts with the input shaft. The torque is received from the drive shaft and transfers, via the input shaft, into the power divider where the torque is divided equally between the front and rear differentials. The power divider, when operated in the unlocked position, allows for speed differences between the front and rear tandem axles while providing equal pulling power from each axle of the tandem. With the power divider unlocked, a tandem axle truck can completely lose traction by spinning one wheel on either axle. Locking the power divider, improves traction by locking the front and rear drive shafts together, forcing one wheel on the front and one wheel on the rear axle to spin out before the truck loses traction. On trucks equipped with two full axle locking differentials, all four wheels are required to spin before traction is lost. In the power divider torque is transferred equally to the pinion shaft of the front differential and the thru shaft, inter axle drive shaft and then the pinion shaft of the rear differential. The torque then travels equally into the ring gears of both differentials - which are attached with bolts to case halves. The case halves enclose and drive the side gears that the axle shafts are inserted into. Finally, the torque is transferred from the axle shafts into the hubs, wheels, and tires.

The reason for increased tire wear and lack of traction on the rear drive is that the rear drive axle is hindered by trailing the front drive axle, meaning it has to react to the changes in road surface right behind the front drive axle which has already achieved the task. The rear axle has little time to react to stay in contact with the road as well as the front drive does. The rear drive also often gets hung off the ground by the front drive axle on very uneven terrain.

Yes, I'm aware of International and their parking system.

​

 

So you're saying the owners manual contains outright lies then?

I know a driver who once forgot to unlock the divider and then ran down dry highway with it engaged. He made it about 50 miles at highway speed before he ended up on the side of the road with a destroyed rear. It absolutely does harm to run down the road with the power divider engaged.

 

What Bender posted is how it works. Here's a link:http://www.desitrucking.com/understand-your-power-divider

 

Got my CDL in February '12...started driving a month later. I am so impressed with you "real pro's" verbally, and with technical prowess, duking it out over out matters such as this. THANKS for all your knowledge shared.