Just turned 2500 mi and am going to change the fluids in the diffs. Picked up 4quarts of Mobil 1 75w90 for the rear and 2quarts of valvoline dura blend 80w90 for the front. It is a synthetic blend. Since I have an 07 lbz the manual recommends 80w90 in the front. Has anyone used this Durablend before, and is it safe for the truck? The guy at autozone said it was real good but just wanted to double check. I know I could have went with the mobil in both diffs but I am trying to follow the manual as close as possible. Any help would be appreciated. Thanks. Also, do I just drain and refill or do I need to remove the pumpkin?