We just bought a 2010 2500HD about a week ago, and we did our first tow down to Austin and back. Truck had just under 600 miles on it when we started. Trailer is a open deck car hauler. Total weight with the track car is a bit under 5k lbs, so not a heavy load for the 2500HD. Former tow vehicle was an 05 Tahoe Z71 with 3.42 gears. The Tahoe had a tune on it, as towing with the 3.42s and 6k lbs (trailer, car, and spares) was not the optimal setup; however I could manage 12.5-ish MPG if the road was not too hilly.

We left late, so I was in a bit of a hurry down there so mileage suffered. Only 10.8 MPG down, but on the way back I drove about 10 MPH slower and the wind wasn't blowing nearly as hard. Managed 15.0 MPG on the way back. I was really disappointed going down, but I'm happy with the mileage coming back. Hopefully it gets better, as I've read a few posts of people getting better fuel mileage as they accumulate mileage on the truck.

I did notice that if you connect the trailer while the truck is running, the integrated trailer brake controller says there is a wiring fault and will not activate the trailer brakes, but the lights will work. Once I shut off the engine and restarted, the trailer brake controller recognized the trailer and everything worked smoothly from then on.

So overall, I'm quite happy. No more downshifts on hills/overpasses, it pulls the trailer on surface streets as if it's not even there, and mileage coming back was very good.

Here are a few questions:
1. The 2500 wandered quite a bit more than our Tahoe. On the way down, I thought it was due to the significant cross and head winds; however it was doing the same on the way back. I'm thinking the alignment may be suspect. I have the same tires on both the Tahoe and the 2500, so I don't think it's the tires.

2. I probably put a little too much tongue weight on the trailer on the way down, as I noticed the truck was porpoising more than I expected. On the way back, I put the car further back on the trailer and this seemed to eliminate the porpoising for the most part. On the Tahoe, I installed Bilstein HD shocks and Air Lift rear coil bags and that took care of the porpoising almost completely. I'm thinking of installing Bilstein 5100s on the 2500 to help, but I don't think it'll need air bags as the suspension doesn't squat nearly as much as the Tahoe's. Any opinions?

3. Even with a fairly light load, I had to turn the trailer brake gain up to 8.5 to get a meaningful amount of brake feeling from the trailer. Is this normal? The trailer is a tandem axle with brakes on both axles. With the prodigy brake controller on the Tahoe, I had the gain turned down quite a bit on B2 and I could feel the trailer tugging on the truck when applying the brakes. Perhaps the integrated brake controller just worse more smoothly so I didn't notice it as much?

4. I'm hoping to upgrade to an enclosed 24-28 ft enclosed trailer next year (probably tag instead of GN); likely 10k lbs fully loaded with the car, tools, spares, etc. Would a Reese WD hitch with sway control be a good upgrade over a non-WD hitch setup with such a long and heavy trailer? If I were to pass on the WD hitch setup, would the truck benefit from air bags in the rear?

5. With an enclosed trailer (likely 6" to 12" higher ceiling than standard), I'm hoping to get 12 to 13 MPG. Is this realistic? Since the truck is fairly new, I'm not planning to do any mods that will void the warranty. Maybe after a year or two. :)

billy
i tow a 24' TPD with my race car inside, totaling about 10k.
truck is 09 duramax 2500 with reese WD and cam anti sway.
no propoising ever. no matter how i park the car in the trailer.
you will not get 12-13mph.
i get 11 at most, avg distance 150miles tow. 65-70mph

I would say your trailer brakes are out of adjustment. Mine GRABS at 5.5-6 on the DIC. My toyhauler does the porpose thing, thats what air suspension is for. Enjoy your truck.

Thanks guys. I'll look into adjusting the trailer brakes, but they work great when hooked up to the Tahoe. I'll have to look into it more, though.

As for towing an enclosed trailer, would a gooseneck trailer prove to be more aerodynamic (and hopefully improve mileage)?

I have a 33' enclosed V nose car hauler. I have not pulled it with my 07 CCSB yet, but put on lots of miles with my 03 ECSB. Your truck will handle the trailer you described easily, but I say get the WD hitch. I towed mine for a long time without one, thinking that I didn't need one.
Finally I borrowed my brother's just to see if it made a difference.
I will never tow without one again! It really makes the trailer pull straighter and feel much more solid.

I pull a T23 Salem Lite that has the aereodynamics of a brick. It weighs about 4500 lbs so the truck doesn't notice it much. We bought the truck last year and I used the WD bars that were required on the old '98 K1500. This season, I have been leaving the WD bars off with only the anti-sway device on and found that overall, there is little difference. Likely due to the new-to-me LMM that already had air bags that the previous owner pulled a 5er with.
When we replace the Lite with an all season trailer, I may likely need the WD bars.
IF I can keep the speed between 55-60, the mileage is between 12-13 inspite of the elevation changes here in the Eastern Sierras.
Note: It's the first time I have ever had to be careful about going too fast up I80 from Sacramento to Reno...:)

my ????? is why doesnt the trailer brakes work when you connect the to the truck while its running......that is a major PITA and shouldnt happen...having to shut the truck off and restart once the trailer is connected makes no sense......any thing in the owners manual or what does the dealer techs have to say???

my ????? is why doesnt the trailer brakes work when you connect the to the truck while its running......that is a major PITA and shouldnt happen...having to shut the truck off and restart once the trailer is connected makes no sense......any thing in the owners manual or what does the dealer techs have to say???

My 2007.5 works fine. I leave it idling when I hook up all the time and when I plug it in I get the 'trailer connected' and the brakes work fine. I've heard of this situation before though and I wonder if there's a reflash some trucks have had to fix it.

my ????? is why doesnt the trailer brakes work when you connect the to the truck while its running......that is a major PITA and shouldnt happen...having to shut the truck off and restart once the trailer is connected makes no sense......any thing in the owners manual or what does the dealer techs have to say???

When plugging in hot, by the time I do the last walk around and get back to the cab, I don't see any errors. I think I saw the error some time ago but I don't remember the cause or resolution.
I do get a "check wiring" or something similar sometimes after washing from the water.

I think I have heard about gain problems with the ITBC. Diesels do get better mileage after break in. R&T even talked about it on the VW TDI.

my ????? is why doesnt the trailer brakes work when you connect the to the truck while its running......that is a major PITA and shouldnt happen...having to shut the truck off and restart once the trailer is connected makes no sense......any thing in the owners manual or what does the dealer techs have to say???

I didn't find anything in the manual, but I didn't look very closely. I haven't taken the truck in for any warranty work yet (and hopefully I never do). I need to try another trailer to see if it does the same thing. I really prefer to do my own troubleshooting and figure out the issue before I take it to the dealer. That way, I know if they're BS'ing me. :)

I did find some instructions online on how to adjust electric drum trailer brakes. I need to give that a try on my trailer and see if it helps.