[Glen_T]

My shop manual shows it to be a pretty easy job. There are two drain plugs on the front side of the rear differential unit. They look to have an internal hex on them, but I'm not sure. The lower one is for draining, and the upper one is for filling. The torque spec on both is 23 lb-ft.

It mentions to use synthetic gear lube from GM, so you might call your dealer and ask what they require. It says to fill it until it just runs out the upper hole, then plug it. It then says to make multiple very sharp left and right turns to distribute the oil to the left and right housing, then re-check the level.

Are you sure it needs replacement? How many miles do you have on the van?

Hope this helps...Glen