what should I do. I have 11k miles on the truck, I haul heavy loads with this thing all day every day 25+k gross weight. I just checked the rear end oil & found that it was 1 1/2 qts low!!! I & anyone that has ANY automotive knowledge knows that you fill a rear end until it starts coming out the fill hole, but what is the dealer going to tell me? I do not want to go in there only to have them tell me that is GM's specs. I think I am going to request that they pull the rear cover with me standing there to see if there is any metal that comes out of it from excessive wear. what do yall think?

I think your pi$$ing in the wind, but it's worth a shot. I'm sure it is better to have the diff filled, but I really don't think GM would put less oil in there knowing it might cause a failure anytime in the next 100K.

They come low from the factory. If you haven't changed the fluid since new there will be a ton of metal in there. The dealer will most likely show you that they don't fill them to over flow anymore. IIRC it's .5" below the fill.

Yeah just change it and fill it right...

Some of the larger axles have a tolerance of around an inch below the filler hole. They are filled by volume through a meter, not to a certain level.

If I were you and I was hauling that kind of weight everyday I would pull the rear cover off, clean it out, put on a Mag-Hytec diff cover, and then refill with 8 qts of 75-140 synthetic. Well thats what I did. My .02-

When I bought my brand new 01 3500, I had the dealer check all of the fluid levels, both front and rear diffs were low (also 1/2 quart low engine oil). They topped them off and after 500 miles of in-town driving and 1000 miles of towing my 5ver, I replaced the the oil in the front and rear diffs. Like was mentioned above, if you are towing that heavy all the time, I might seriously consider investing in an extra capacity rearend cover and change oil annually.
JP

Its true they dont come full from the factory, GM says its ok. I have the guys top off the rear diff during the prep. It saves the phone calls and walk ins for people that are board enough to stick there finger in the fill hole :D .

Its hard to sell people on the fact they dont have to be full.