What did the rear springs look like? We had ours nearly flat on the move down... and that was the SMOOTHEST ride I've ever had in the truck!!
Agreed, the military rated the truck for 5 tons on road - but the military usually builds in a buffer to the ratings, so that putting 10,001 lbs in won't instantly cause the truck to self destruct. These trucks can handle more than that, as evidenced by their towing capacity. The deuce can tow another 3 tons, even when fully loaded!! But they can't handle more weight + normal top speed + curvy roads + stopping on a dime, etc. The point is, if the truck doesn't stall when you put it in 1L, then you can handle the load. You just need to understand what constraints that places on your driving capabilities.
USMC6062 - The transfer case is synchro-ed in both ranges, because shifting on the fly is necessary when loaded (otherwise you'd have a limited top speed). However, the high and low ranges overlap a little bit, so it's not like you go from 5L to 2H. Jwaller's explanation is right on the money for where the gears line up - from 5L it's best to go into 4H, and then 5H. The best solution is to drive your truck, and get a feel for it on your own!
There is a very cool "Multifuel Operator's Manual" from the PS magazine section that is pretty informative regarding driving habits. It's
here.
Also, the manual number 9-2320-361-10 is titled "Operator's Manual," and covers how to turn on, drive, stop and turn off the truck. It's
here.
Below is an image of the shifting speeds dataplate from the -10 manual.
Matt