something getting loose in the drivetrain

[Chamberpains]

The missing link, I see a lot of problems with running the power divider locked in all the time. The biggest 1 being catastrophic failure due to losing traction and then violently getting it back especially while turning. Spin out situations, unhooking from a trailer and turning at too fast of a speed are just a couple examples. Instead of having each axle shifting power from left to right on their own terms, you now have them trying to work together while the power divider is in. That causes a lot of gear stress in the power divider or weakened components. I've replaced countless rear ends because of this. Most of which came in with the pinion shaft sheared off because of the violent power change between the axles. It wouldn't take out the power divider very often.(which you think it would being it's the smallest set of gears)

Then there are speed differentials between the two axles that can't be compensated for when the power divider is locked in.
The biggest one is mis-matched tires between the 2 axles. There is only so much backlash setting in the gears to compensate for slight differences. If the two axles have different size tires or one is new and the other is worn more. You'll get gear sets riding on the back side of the teeth or none torque side which will burn up gears in a hurry. They are out of time with each other, plain and simple.
Now, some guys can get away with this for a period of time. Because of extra slop from extra wear in gears and components or larger backlash settings. But even then your putting stress in places where its not designed to take for long periods of time. It's gonna cause some premature failure.

Picture your axles as if they were 2 brothers connected by a steel shaft to each other. They obviously will never want to or can't walk the same speed as each other. Take a second and imagine these 2 brothers tied to each other the chaos that ensues when something happens like 1 brother slips, or trips. The same thing happens with your rear ends and gear trains. You run the risk of these two brothers not getting along at some point in time for whatever reason then you will have problems. So why not let them work individually from each other as much as possible.

I think it's sheer operator laziness if you can't flip a couple switches multiple times in your day to get the job done and still get longevity out of your equipment. All you have to do is become an actual driver and assess every situation (sometimes down to a second by second basis) all day and adjust to it. Don't rely on your truck to compensate for everything. It just can't and will fail.

Now with that said, I also know that every moving operation is different. If it's in your business model or operation model to tear drivelines out to get the job done (like timbering, field harvest and any place that requires constant shi#t traction conditions, which there are better ways of getting trucks in and out of these places ie; pull trucks or equipment) then get at it. Cause there is no money in not getting the job done.