My truck (2001 GMC Sierra Z-71 4x4) will be hitting 100,000 miles next year (summer). I just think it is a good idea to know what is going on in my truck so I was thinking about getting some of the fluids analyzed. What fluids should I get analyzed? I do NOT plan on getting an analyses on the brake fluid or the power steering fluid. I flush the brake system every year, and I change power steering fluid when I do an oil change. I was think about getting the transfer case oil (autotrack) checked and the engine oil. There is also the front and rear differential fluid and the engine coolant (LowTox). I am figuring to spend up to $100 for all the tests.