I'm still not sure on breaking strength of my cable but the factory rating on the winch seems to be 3600kg for what it's worth.
3600kg would be roughly 8,000 lbs. of pulling force, so a 5/16" wire rope (if that is what you have) would be fine.
(New) 7X19 galvanized aircraft cable has a nominal breaking strength of about 9,800 lbs. and will probably go a bit more before breaking.
The pic. of the winch posted above shows a very rugged looking unit. Judging solely by looks....I'd be inclined to think it was capable of an 8,000 lb. pull on a single line (first layer on drum).
But, the Toyota info provided ..suggests that it will pull only 2,200 lbs. on a single line and that more pulling power can be had by doubling or tripling the line.
If it was Toyota's purpose to restrict liability to themselves, then I submit they went about it the wrong way.
If the consumer is NOT to exceed 2,200 lbs. of pull on a single line...then Toyota should have provided some way for the consumer to measure/gauge/meter the amount of strain on the unit.
Otherwise...they have only succeeded in "duping" the user into thinking they are pulling less than they really are.
You can tell by looking at the winch...it is not "wimpy" (unless it is geared weirdly or has a weak motor).
Very odd consumer info IMO.