At our pick-n-pulls, gas and coolant must be drained, but that's about it. Wheels stay on until they're sold or the remains are crushed. Transmissions and axles seem to be left alone. Batterys are removed and properly recycled, they usually sell the ones that are in good shape. In fact, the yard I go to most often drains coolant and washer fluid, filters it, and sells it cheap.
