Posted by 97-k1500 on September 22, 04 at 23:15:46:
In Reply to: Re: Should I drain differential after adding dino oil to the synthetic? posted by Bish on September 22, 04 at 14:51:31:
A bent piece of wire or coat hanger will also serve to check the oil level. My regular mechanic sees many leaky diffs on the GM trucks. He says many of his customers have this problem soon after visiting the quick lube. The old rule of thumb was to fill unitl the oil dripped out of the filler hole. He believes this is what causes the leaks. GM didn't go through the trouble of editing the owners manuals to say fill to 1" below the fill hole just because it was fun. I lower the truck (using a jack) and place the left tire on a wooden block and the right on the floor. I fill until the oil comes out of the fill hole. When the axle is level the oil is about 1/2" below the fill hole. You can experiment. I would siphon out any extra (to meet the correct level spec) with some vinyl tubing.