When using a winch the first thing I would suggest is to work out the EP or estimated pull this is done by taking account of the following;
1 Ground Factor ie nature of the ground you are on ie deep mud offers greater resistance than wet grass, for deep mud I would allow the weight of the vehicle devided by 2.
2 Damage resistance ie a locked wheel will offer greater resistance to movement than a free rolling wheel, I would allow 25% of the vehicle weight per locked wheel.
3 Gradient resistance ie if on a slope up to 45 degrees allow a proportion of the vehicle weight per degree. over 45 allow the total weight
of the vehicle.
4 Safety factor, the above figures are estimates so total 1, 2, 3 devide the result by 4 & add that result to your total figure the result will be your estimated pull or load. ie GF + DR + GR totalled Plus SF = EP
Winch pull capacity; The rated pull will be quoted on a drum with only 6 coils approx on the drum, as the drum fills up the pull capacity will drop dramatically. I would recommend that where possible you ALWAYS use a snatch block this slows the pull down but doubles apprx the pull available ie an 8000 lb winch can pull 16000 on the first wrap of the winch. Bear this in mind when selecting an anchor point!
You may find that you have sticking brushes in your winch at present which may account for the apparent lack of pull.
Last; Wear Gloves & count your fingers. Happy winching
