The function of installing lockers is because sometimes you do need this feature, (i.e. Rock climbing) just like sometimes you are good without it (i.e. Mud) just like sometimes you don't need any (normal pavement).... Because sometimes is good to have all wheels locked and sometimes not. Have in mind (pro rock crawlers pkease correct me if i'm wrong) that when rock crawling, not 100% of the trail the lockers are engaged. They engage them only when needed (i guess you dont need that much stress all the time).

 

correct you dont have the lockers engaged at all times.. only when needed, or you think you need them..

 

This is a good explanation that I will expand upon.

Everything you said above is true. Furthermore, the path between pairs of wheels, either front or rear axles and left or right sides, are also different. The inside wheels will always track on a smaller circle than the outside wheels. And unless you are drifting, the front wheels will always track on a larger circle than the rear wheels on either side of the vehicle.

For example, when negotiating a U-turn to the left, the smallest circle is made by the driver side rear tire, the next largest circle is the driver side front, the second largest circle is the passenger side rear, and the largest circle is made by the passenger side front.

The differentials can take care of this discrepancy between pairs of wheels on the SAME axle. However, part time 4wd systems are directly connected at the t-case, and if you understood the example above correctly, the the front wheels are rotating at a different rate than the rear wheels, hence the surging/clicking/binding that happens when you have 4wd selected on high traction surfaces.

AWD systems have a third, central differential, usally at the transmission itself, to bias the axle velocities between the front and rear axles.

I work on turning radius drawings for trucks and buses so I'm quite familiar with turning radii as we have to design fuel depots and maintenance yards so that these rigs can make it into the compound without scraping walls, buildings, etc...and I hope I have clarified a few things as well.

 

Furious Filipino,

Yeah, I went into only the front-to-rear aspect because the guy I was responding to already understood the right-to-left aspect.

Interesting what you are doing for work. People don't think about the planning that goes into such things until poor planning shows it ugly head.

 

Probably already said but...

Differentials were created to allow vehicles to turn. One tire (inside say) must spin a ta different rate than another tire (outside say). In a light 4wd mode...(defintiion differs by makes) there is some control of this to prevent weird results when in an extreme situation.

Example...differential wants to allow outer tire to spin differently than inner tire so you don't wear tire abnormally. Then you find yourself with one tire in the air and it is spinning very well while the tire in the mud is still.

If you can lock the "differential" then essentially you are removing the "differential" and making it a "samerential" where all tires get same power and spin the same. This is advantageous off road most of the time when stuck. It is bad if you are running down the road for some weird reason in 4wd on a pretty day on asphalt (usually because you think 4wd is the same as AWD for a Honda CRV). I had a LC with rear/front/center differential locker ability. It could get through some stuff when it was fully locked.