What can cause oil hub caps to melt on a kenworth steer axle, when wheel bearing have been replaced and are set correctly,
How are the bearings set? Do you have a measured 0.01-0.05" end play at the spindle? If not it's too tight. Your other possibility is the brakes dragging and building up heat. Why did you have the bearings replaced in the first place? was it a heat related failure?