Here is what I know about it. The rear differential affects the speed of the driven wheels. The driven wheels turning at different speeds is what helps the car rotate through the corner. When the driven wheels turn the same speed (differential fully locked) the car has a harder time turning making you understeer. The power/coast/preload settings in the differential help fine tune this to your liking.
Power is the amount of force to lock the driven inside & outside rear tires together when your on the throttle (accelerating). A higher number will make the car tighter (understeer) on throttle. So if your loose (oversteering) on throttle then increasing the power setting can help the situation.
Coast is the amount of force to lock the driven inside & outside rear tires together when OFF the throttle (coasting). A higher number will make the car tighter (understeer) when off the throttle. So if your tight (understeering) on corner entry when off the throttle then decreasing the coast setting can help free the car up & turn better.
Preload keeps your differential locked (inside & outside wheels turning the same) until the torque differential equals or overcomes what preload setting you chose. Basically the higher the number the longer it takes for the power & coast settings you selected above to take effect.
Take all this with a grain of salt. This is what I've learned over the years but I could be completely wrong, lol.
As Aaaron said, the Power setting effects the car under acceleration, therefore adjusting this setting will change the car's behaviour on CORNER EXIT.
The Coast setting effects the car's behaviour while you are off the gas, in other words under braking. Therefore the Coast setting is to do with CORNER ENTRY.
The differential is one of those subjects thats most difficult to grasp imo, especially when trying to understand ramp angles, but the best way to figure anything out is just to keep fiddling with it and see what happens.
Coast is the amount of force to lock the driven inside & outside rear tires together when OFF the throttle (coasting). A higher number will make the car tighter (understeer) when off the throttle. So if your tight (understeering) on corner entry when off the throttle then decreasing the coast setting can help free the car up & turn better.
""""Power is the amount of force to lock the driven inside & outside rear tires together when your on the throttle (accelerating). A higher number will make the car tighter (understeer) on throttle. So if your loose (oversteering) on throttle then increasing the power setting can help the situation""""
