Found this,,,,the link gives a table for ground effect percentages,,,and effort required,,,,,
Calculating Winch Loads
Total Weight = Vehicle Weight + Load weight
Winch Pull = ( <Slope degrees> * Total Weight /60)
Ground Factor Weight = Winch Pull * Ground Effect Percentage
Winch Load = Winch Pull + Ground Factor Weight
Example. Given:
* Vehicle weight = 4,400 pounds
* 300 pounds of total load weight
* winch up a 50 degree slope consisting of shallow mud
Total Weight - 4400 + 300 = 4700
Winch Pull - (50*4700/60) = 3917
Ground Factor Weight - 4,700 * 35% = 1645
Winch Load - 3917 + 1645 = 5562
http://www.4wd4all.com/forums/attachment...012&thumb=1