Difference between 2H and 4H AUTO on dry roads?

[ParadigmDawg]

All this talk made me go out and try my TRX in 2wheel drive. I have a Tazer married already so in turns on 2wd just by holding in the TC button for 10 seconds. I never new 37 RGs would light up so easily and produce so much smoke.

It was a kick but I hope I don't do it again but I don't trust myself.

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[Zandcwhite]

A agree with what you are saying, and to be clear I did not say otherwise. The start of the conversation deals with why 392 Wranglers had 4 Auto and no 2wd mode and the affect on the road. My comments were stating that fact that 4 Auto transfers at least part of the torque to the front wheels in those conditions and thus less total torque and stress to the rear axle.
I will agree you are much more likely to break and axle when in 4 low and bouncing around under full throttle climbing hills and such for reasons stated above. My original comments contradicted the statement that ALL of the increased torque from the low range gearing went to the rear axle but was rather split front and rear. Yes, there is more torque going to the rear axle in 4 low, even with a 50/50 split, when in low range...but it's only around 137% increase and not 272%. Just for reference I have had a trail rig/rock crawler for 20 years with 1-ton axles (Dana 60 front) and have broken several "stock" front axle shafts (both inner and outer). Currently run chromoly front shafts with upgraded 35 spline outers. I have also broken several "1/2 ton" front axles over the years so very familiar with this situation.
In regards to the axle size difference my previous posts was referring to the exact same model vehicle (in this case talking about the 1st gen Durango's to be specific) with the only difference being one had a 2wd mode and one did not have 2wd and only 4 auto/AWD. The version with 2wd would grenade an 8 1/4" rear axle several times during a Powertrain Durability Test. However in the AWD version the same axle would survive the entire test. I worked for many years as a test engineer at an automotive proving grounds. Obviously the the weight of the vehicle and towing capacity between completely different models plays a role in the size of the axles. That is why I made previous comment that comparing a Wrangler 392 versus Challenger Skat Pak rear axles wasn't an apple to apple comparison. The comment was made that the axle was sufficient for the Challenger so it should be sufficient for a 392 Wrangler. I contradicted that statement because the Wrangler is much heavier and had larger tires.
Again, I agree with everything you said above.

Breaking axle shafts in old, low powered rigs just proves my point about the idea of the torque being split equally front to rear and/or side to side with lockers on. Broke several Dana 60 shafts in my old xj, with a whooping 224ftlbs of torque and a shit crawl ratio of 33-1 on 37s. At the wheels that's only 7,300ftlbs of force, divided in half it isn't enough to break a Dana 60 shaft let alone divided by 4, so explain how it's possible? If only 1 wheel has traction, or gets almost all the power as the only power being used by the other 3 is what it takes to freespin a wheel and tire which is virtually nothing. I'm not arguing you couldn't break a shaft in 2HI, only that you're more likely to do so in 4LO in both my experience and the math. Dividing the torque by 2 only happens if there's equal traction between the front and rear, which is why awd Durango's survive the testing on road as they pretty much always have equal front to rear traction.