Originally Posted by SLE

I've pondered this and I suppose if it was a dedicated tow rig 4.88s would probably be better under certain conditions however you need to decide how much weight you plan to tow, what speeds you want to travel, how often you tow, and what terrain will you be traversing. There's a trade off no matter what you do.

For me I tow 14k-15k lbs about 6-8 times a summer at no more than 100 miles or so each way. I tow 8k + lbs probably an additional 1500 miles and less than 8k lbs another 500 miles. The remaining 2-3k miles a year is spent running emty hunting or for small loads that I need a pickup box for be it furniture or what ever. So I total about 6k-7k miles a year with about 1/2 of that towing some type of trailer that's likely at or above 8k lbs. When towing heavy (more than the fifthwheel @ 11k lbs) I tow at speeds around 60-65 and otherwise I like to cruise around 70 mph with less. When emty I push towards 75 mph on the highway and I don't use it around town as a daily driver very often. Terrain wise I run mostly rolling hills but I find the wind to be a larger factor as it seems it's alway blowing 20mph against whatever direction I'm driving. For me 4.56s were a trade off between getting the RPMs where I can tow occasionally in OD and have the RPMs between 2200-2500 and in D when the going gets tough with the rpms between 3000-3300 or so. This works well for me. With 4.88s it would put me at 2600-2700 rpm in OD at 75 mph which is probably 1/3 of my total mileage every year. The way it is with the 4.56s I'm already pushing 2500 rpms at 75.

Also, 4.88 would render 2nd gear almost usless if needed when pulling a load up significant hills at higway speed. 2nd at 65 mph would put you over 5000 rpms. Also towing in 3rd at 70 mph would yield 3,500 rpms which is getting a little high to run if you plan to do this for a significant amount of time. The 4.56s put me at about 3250 at 70 in D and as I found, it pulls very strong when setup like this, however fuel mileage suffered greatly.

All of this is of course assuming the use 285/75/16 (32.8") tall tires. Right now mine are just about wore out and I do notice my rpms a slightly higher than what the calulator shows. It really comes down to how you plan to use your truck and what things your willing to compromise.