Oil - 3000 to 15000 miles, depends on the oil you use
Auto trans - every 30,000
Differentials - every 30,000
Transfer case - every 30,000
Dexron - says 5 years or 100,000 miles.......I do mine every 30,000
DOT3 - 3 years or 30,000 miles
Power Steering - I do every 30,000
Those intervals are what I do. My truck is a 2004 that I have had since new. I'm still on the original motor, transmission, rear end....never a problem with my G80, original radiator, original power steering pump and the brakes I redid for bigger and better.
I also get 27-30 mpg in a CC 3.5, auto and 3.42
So take what I say for what its worth......but its working for me
Thanks man I appreciate the info, I'm avg. 20-21 mpg though I have the 3.73 not sure if thats the big difference but 25+ would be great. I have an 05' also original owner I'm right under 85k, I somehow lost my maintenance records so I'm gonna bust it all out at tax return.