mightymouse said:
Hauling heavy loads can shorten the transmission's lifespan.
The #1 cause of transmission failure is heat.
If you plan to tow often, an aftermarket trans cooler is the way to go.
X2 on this, for sure. Heavy duty usage requires a little bit of heavy-duty retrofitting. Oil and trans coolers will help dramatically. Conversely, those who just use their trucks for the occasional haul or offroad will probably not have too many issues. My 00 Yuke has 84K miles on it and it runs fine, shifts great. My father in law's 02 Suburban has over 150K, and runs like the day it came off of the assembly line. Go figure.
If you haul or hard-use your truck, get a pretty decent sized trans cooler, but have it PROFESSIONALLY installed. Trans heat is the number one killer, but no trans fluid comes in a close second - which is exactly what you'll end up with if one of those cooler lines comes loose and dumps your fluid everywhere.