BILL J. - Yes, CC rearends are stout! But I would NOT go jerking around on stuff, especially with chains, tow straps are designed for that type of use, but they still scare me. Because they stretch, if the come unhooked or break the end becomes a missle headed straight back to the pulling tractor.
I've only ever heard of ONE CC having a rear axle carrier breaking, an early 982 that belonged to the guy my QA-36 snow blower belonged to. He had a scale model of a rear mounted snow blower he made from scratch on the 3-pt of his 982 powered with the rear PTO, it was HEAVY... and he got stuck in a ditch or something and whle trying to rock the tractor back & forth to get un-stuck broke one of the die cast axle carriers.
When I built my sleeve hitch 30 yrs ago I made brackets to attach the hitch to the axle carriers. That distributed the draft force over a much larger area of the rearend, just like IH did with their full size tractors. Putting all the draft load on three 3/8" bolts is/was not the best design. Like Vince said, pullers use at least two more 3/8" bolts on the top of the rear cover. A puller's design criteria is/was different than I was trying to accomplish so my design was made to reduce loads on the whole rearend instead of maximizing weight transfer.
Not sure what the limit of draft load is on a hydro, but I've been told on a gear drive, in a "Perfect World", no slippage at ALL anywhere, the top shaft in the trans can twist in two around 15 HP. Stronger top shafts are readily available, and over-drive reduction gears also increase the HP potential of that shaft by whatever percentage the speed increase is. IH's biggest GD was 12 HP until the 16 HP 582 was built, but MTD made an 18 HP, the 1806 model, IH 3-spd w/creeper. So with less than perfect traction, the IH rearend can handle a L-O-T. The gears & shafts in that rearend look more like what you'd expect to see in a 6-cyl. car like a early Chevy II, Ford Falcon, or Dodge Dart. Some pullers do use a Dana diff in their pullers, but the weakest link is the cast iron bearing caps that hold the diff carrier inside the rearend. Aftermarket (MWSC) aluminum carriers handle the abuse of pulling MUCH better, not near as brittle.
One of the design compromises made by IH in using the CUB rearend was reducing the input speed of the transmission. On the CUB, the trans ran at engine speed, 1400 to 1800 RPM depending on the model, the GD CC has a 7:1 reduction in frt of the trans. The CUB was only rated 9 to about 12-13 drawbar HP, so the trans sees more actual torque in a GD CC than a full size CUB.
Not sure how that all compares to your off-color tractors, but if the the old 70 SON is mowing with this summer is any indication, 48+ yrs old and NEVER had a transmission part replaced... EVER.... wore out at least FIVE K161/181 engines, I'd say the old GD CC's are as durable a garden tractor as was ever built. Those homely Economy Power Kings were in the same league, but I wouldn't say they were any better.