Not so. Either gear sets will be fine from a stop. Pulling a grade may find less downshifting with the 4.10's vs the 3.73's, especially if you keep it out of trailering mode. Keeping it out of trailering may result in higher fuel mileage. I think the weight of the boat puts it right on the border of whether trailering mode should be used or not. I DO NOT use trailering mode towing my 226 Cobalt (probably close to 6k lbs). There is enough power and gearing to not lug the engine.

Pacesetter, do you know the tire size with either gear ratio options?

Trailer mode increases the fluid pressure in the transmission, thus helping handling the stress/heat. At least that's what I was told. I use TowHaul on the highway with our 04's Tahoe Z71. Keeps the torque convertor locked up. In town, I flip it off.

I don't think 4.10's are going to prevent a downshift on a long grade in the Ozarks. Those are some fairly long steep mountains/hills.

I have a 2007 NBS 6.0 with VVT 4 speed auto & 3:37 gears and pull a 5200lbs.(dry) Stingray 240CR. The 6.0 has plenty of power once you get past the 4 sec. torque Management delay.
Get 10 mpg pulling interstate 65-70 mph.

3.42 or 3.73?

I get 12 mpg pulling my Cobalt 65-70, with the old 6.0L 4-speed 4L60e and 4.10's (go figure), which was 50% better than either one of my Ram 1500's 5.2 or 5.9 gasser returned (8 with those).

And again, I do not use tow/haul mode, as it lets the engine rev too much and the trans downshifts too quickly. Tow/haul mode would be better suited for heavier loads. I leave it in overdrive, and put the cruise on if traffic allows. I plan ahead for the hills or traffic. The trans temp never gets above 200°F, and I service the trans once a year in the spring.

What works for me may not work for someone else.

You do have a bigger engine and better gear than our Tahoe has. Our Tahoe won't pull the our boat 65-70 with the cruise on unless it's 3rd. It's too much for O/D to handle at 2,000 rpms. I've noticed T/H holds gears longer before forcing an upshift. Example, If i'm motoring along around 68 and hit a small incline, and my speed slowly tapers off to 62/63 while i'm pushing the throttle to the brink of shifting, with TH on, it will keep it locked in O/D and allow me to slowly deaccelerate. With T/H off, it gets upset and start unlocking the T/C or downshifting into 3rd unless I back off the throttle (which I don't want to do). However, if I quickly react with the throttle, it will immediate force a downshift. The other nice thing is that when a downshift is needed, T/H does a good job of holding 3rd under lighter throttle until I get to my desired speed. So, I suppose T/H is a two way street. And something to remember is our Lowe, although lightweight, it like towing a freaking kite with air resistance. We get 9-10mpg towing. If I drive 55, I can get 11mpg.

At any rate, this is obviously not going to be a problem with a 6.0L engine. And given that your 6.0L with 4.10's and 4 speed auto does a very nice job with 6500lbs or so, then it stands to reason the newer, more powerful 6.0 with 6-speed should be exceptional with 3.73's.

But, you know, when in doubt, go with the 4.10s.

D

Well I purchased the Silverado 2500,4X4,crew cab,vortec 6.0L,w/6speed trans,4.10 ratio Monday. It seems like it has plenty of pep. I was surprised to see that at 70 MPH the tach reads 1800-2000 RPM's with that gear ratio. cny boater, the tire size is LT265/75R17.I will be driving it this week to get some engine breakin. This weekend I hope to trailer the boat to a local lake. There are some pretty steep grades (nothing like the Ozarks) I will see if I need to use tow mode or not! Thanks for the great information that I couldn't find using Google!

Congrats!!!!

Hey. Read your owners manual. There is a break in tow period too. No full-throttle starts and don't exceed 55mph for X number of miles. It's probably worth considering to follow. And...I don't think you're going to notice the boat is back there!

I probally need to slow down and read the manual. It's been a busy time locating and puchasing this truck. I still need to get the new trailer wiring plug that will adapt to the new truck. I can't wait to get the boat to the lake and enjoy some time on the water!!!!!

Just skip to the towing section. It'll take about 5 minutes to read.

Congrats Pacesetter. New truck smell......I'm envious!!!

3.42 or 3.73?
Oops! Typo 3:73

SKP05 I have 4.10 axle ratio.

Congrats, Pacesetter. Enjoy the new truck.

I've got an '06 crew cab 2500HD diesel and love it. Even with the $4.65 diesel, I'm still amazed at how well it tows my Cobalt 250. It's just a beast and is perfectly willing to pull the boat much faster than my wallet will allow. Towing the speed limit (up and down the hills) I'm getting 12.5mpg. If I slow to down a little and don't fight the hills it gets 13.3. In daily driving I'm up to 18.4mpg and I don't speed any more.

In reply to silverbullet - the '08 2500DHD's are GMT900 through and through. I'm told there were some parts of the frame carried over from the GMT800's, but they're already on the GMT900 platform.

I've got family that works for GM in Michigan, specifically on this platform. We're headed up there on Thursday and it looks like we might get a chance to tour the Flint assembly plant where they make the crew cabs later this week. If anybody's interested I'll post impressions.