Hey guys, I wanna change the fluids in the rear diff and front transfer case/front diff. But do I need to do the center diff as well? Anway ways, I've heard alot of people just using vavoline 75w90 so is that what I should go with or maybe a Redline product??? I'm going on 204,384 miles so it ain't like I'm gonna throw down some synthetic blend, lol. I do get some grinding when downshifting to 4th on the freeway and 1st is sometimes hard to get into on startup.

Cody