>>4 low is spinning a sun gear and many little gears in the transfer case making it heat up allot!

Many people drive many trucks in '2 low' (4 Low with hubs unlocked) for some distances. As long as you don't romp on the throttle and drive sensibly, this isn't the end of the world. Yes - you can put 2x the torque to your wheels and possibly blow out u-joints, etc., but that's where the 'drive sensibly' part comes in.

I would install manual hubs if did this a lot, to avoid the 'what state is my hub in?' question that frequently applies to Ford's vacuum hubs.

 

Not quite sure I agree with this as a general rule. Maybe for extreme periods of time?
A/T's use the same style planetary gears. And they are used for more than short distances. True, the TC does not have as much capacity or as effective a cooling system, but has more than a differential.
I have not heard of any fundamental weaknesses in these 271 transfer cases... I have repeatedly used mine in low for a couple hours at a time during off road trips and had no issues. And I use 2 Lo quite often when towing on really steep (10+% grades), albeit rarely for more than 15 minutes or so. I have not seen my TC lock in 1st (I have LED that shows when locked), so if I have to go that slow, I go to 2 LO and 2nd gear where it will lock.
The ATF in the transfe case has never come out brown or smelly or other symptoms of overheating.

Note to self: Add a temp sending unit and test it some day! I have temp sensors all over the truck with switches to a couple gauges so I can check various things. Adding one more sending unit is no problem.

 

Well I burnt up two transfer cases by running them in low for a distance (maintained transfer cases mind you). I won't do it again.

 

A transfer case exists for a reason, and there's nothing wrong with using it when the need arises. Moving at slower speed with gear reduction is essential for controlled ascents/descents, particularly wth loads and/or in rough terrrain.

I've done this for years with a variety of 4x4s, including three Super Duties, one of which I currently use and own.

Extended transfer case use is okay. I've gone all day in 4-low with no issues. Watch your temps, particularly in hot weather, since you're at low speed/low air flow, and you'll be okay.

You'll know when you need the transfer case' lower gearing. Not using it puts more wear on other vehicle components, such as brakes and suspension, and may place you or your load at risk.

 

Like anything there are some people that can drive or do anything and get away with it. other have failure.

The transfer case fluid isn't cooled in any way but threw the case. There is also very little fluid in the transfer case which means it heats up very fast. Asking the transfer case to take a big load and at speed for a long distance is just asking for it. Sure you may have been fine in the past but some day it will bite you.

Now just to be clear I am not saying you can't drive any distance in 4L. If you are crawling along and staying under say 10mph I would think it is ok to drive along all day in 4L. But if you are using 4L on the road to drive more than a mile going over 15-20mph it is almost certain some day you will be replacing the case. With a load on the truck or trailer increases gear friction which increase heat. And coming from a guy that has done it and seen it happen there isn't much warning when a case fails. It goes just fine, maybe it will make a little noise for a couple hundred feet or so then stranded like the ford on the trailer with a bad case. Also notice it is winter so it was NOT excessively hot outside.