99 vs. 05 - powertrain differences?

I own a 99 silv. z71 and i recently have driven a 2005 z71 o/r.. aside the physical differences i was wondering if anybody knows of any real differences in the engine, tuning or drivetrain... They seem to drive and operate so differently it makes my 99 feel like poop. Ok so its alot newer and alot less miles but at the same time it just seems So different. Not only that but i was interested in this "tow package" deal thats on my origonal window stick.
Says something about a transmission cooler... ok so where is it? Is it just a larger coolant and transmission oil radiator or maybe the reason my fan is engauged so often? Im new to owning a silverado and i have so many q's about it (my truck)
chris

The tranny cooler is located between the grille and the radiator... get a flashlight and look into the openings of the grille and you can see it. I suppose one of the biggest difference in the year models is something you mentioned... the fan. Yours has a belt-driven clutch fan that saps power. The 05 has electric fans that run off of the battery/alternator. You can convert yours to e-fans, many people do. I hear it frees up quite a bit of rwhp.