I have a 2004 Chevy 2500 quadrasteer . The rear end lube is a special synthetic type. I had it in the shop a few times since new to have the rear end fluid changed out because of a noise when reversing. I have noticed that upon starting from a stop the rear end slips just a bit every now and then. Always at a stop light when warmed up. I figured that the fluid must be low so I went and got some lube from the dealer. When I opened the nut on the side of the rear end ,fluid flowed out. I replaced the nut quickly. The manual says that the fluid level should be 1/4 " below the hole. I was on level ground. The truck was hot. Does the fluid expand ? Do I need to let it cool down. It looks like there is too much fluid in it! Would that make it slip. Truck has 130,000 on it.