It's a good way to break stuff. Two things to consider:
1) Pulling a sled in low gear allows time for the engine to reach peak output. Peak power + lowest gear = maximum stress on the drive train. Not to mention longer time before it stalls...
2) As the load increases slowing the truck to a stop, power is actually going back through the drive train in reverse. Acceleration requires power, acceleration is a change in speed, so to slow something (accelerating it in the opposite direction) means power is going in backward, and depending on how fast the truck is forced to slow down, the drive train could experience way more torque than the engine could ever supply.
In pulling videos, trucks often break just before they stall, after having experienced higher than maximum torque for a few seconds. The weight of the sled, if on the truck, can increase traction such that the wheels don't slip as easily as they would if a driveshaft starts twisting, so it gets twisted until it snaps.
max tq on the engine is considerable less than my clutch or transmission is rated for, first gear isn't a low ratio at all so the diff and U joints should take it
I do agree that it's a good way to break stuff, and was a consideration, especially my hitch thats only rated to 16,000 pounds, everything would most likely be OK
I will be putting either a brownie box in, or if I feel really fancy, a 13 speed Eaton, low ratio's would save lots of wear and tear on everything by not having to use the throttle to get moving, less RPM's = less shock load risk, same for closer ratio's, my synchro 5 speed will either refuse to go into gear, or the synchros will grab and let you shift way too soon resulting in grinding or dropping into gear really hard, specifically 2nd gear, it doesn't care how close the RPM's are, so if you're in a rush to grab 2nd you can get into doing severe damage really quick, especially since its almost an 80% split between 1st and 2nd so you're back to nearly a complete stop before the engine as slowed enough to grab 2nd
You're only about 2 hours away from me, so I figure your roads are very similar to mine, you know the sort of hills I'm encountering, add in living right on the river so we see lots of driveways with 20-30 degree inclines, no clue why people are so stupid as to spend 5-10 million on a house, and have a driveway you can't drive up in the rain, but they do it and think its cool, there was one specific driveway that my bucket truck wouldn't hill start on, 4 speed Alison, not sure which converter it had but it would stall the converter and start rolling backwards, that one sucked to get out of
