I change my tranny fluid and filter every 30K. I got to change the tranny itself at 70k! I did the front and rear ends at 30 and 60k as well. I strongly advise changing your fuel filter every 20k or sooner. Because of fuel injection the filters these days screen out a lot smaller particles. This means they clog much faster making the fuel pump work harder. I came by this revelation when my fuel pump went out at 42k. The filter only had 12k on it and I couldn't blow through it. The pump was $650. The easiest way to change the pump is to lift off the bed. Six bolts, three buddies, two sawhorses, and 1 hour.