Just changed out the front and rear diff oil on a 94' 4runner with 175,000 miles on it. Both differentials had shavings on the magnet of the drain plug. Color was dirty, the fluid stank, and there were fine particles of metal in the fluid. The rear was worse than the front. Haven't gotten to the transfer case yet, but I'm expecting it to be about as bad. Hope it stays together another 100,000 miles...