Hi all, just got back from a 1000 mile trip towing a 8500lb toy hauler up and down the California coast and mountains. I have a 2009 3500 LT 4WD crewcab longbed SRW and never once feared a hillclimb (like I did with my old V10 ), even in the Redwoods or 105 degrees through the twists and turns of Hiway 25 below Hollister on the way to Pinnacles.
A few observations while towing... in TH mode of course. (normal behavor or not?...)
1.Trans temp got up to 192 for a short time once, 20 minutes during the hottest daytime running through some foothills with tight turns. usually trans temp was 90 to 100 degrees above the air temp. 160 to 170
2. Engine temp stayed rock steady in the middle at 210, then on the long steep grades, the trans might downshift into 4th with RPMs at 2300 or so , then it climbed to 230, then the (roaring) fan kicked in and dropped it back to 210. This always seemed to happen at the top of the grade - it's like the truck knew it was at the top! ...weird...)
3. Also my batteries on my trailer were NOT charging while I was driving. I re read the owners manual and read that the Dealer needs to connect the aux 12 volt feed??? located on the harness next to the fuse box....is that true???

Thanks for your input. I love the truck, strong and smooth, it delivers on the promise, nice when a product does that.

Dave in HB

Engine/trans sound normal and yes the 12volt trailer feed is taped up under the master cyl...goes to a post in the fuse box.

You have to manually downshift it on hills to keep the temps from running away. The tow haul mode will lug the engine on hills without enough fan/water pump RPM to keep you cool at anything less than WOT. The sweet spot is anything over 2200 RPM. Even at the sweet spot the fan takes it’s time to kick in while ECT rises. But the manual downshift keeps it from running away too badly.

Should take 1 min to hook up the clearly marked trailer power wire under the hood.

The trans sets a code at 10 seconds at 252 degrees. You have a new fluid that can take the heat. I have seen 240 and no ill effects.

You have to manually downshift it on hills to keep the temps from running away. The tow haul mode will lug the engine on hills without enough fan/water pump RPM to keep you cool at anything less than WOT. The sweet spot is anything over 2200 RPM. Even at the sweet spot the fan takes it’s time to kick in while ECT rises. But the manual downshift keeps it from running away too badly.

Should take 1 min to hook up the clearly marked trailer power wire under the hood.

The trans sets a code at 10 seconds at 252 degrees. You have a new fluid that can take the heat. I have seen 240 and no ill effects.

:exactly: Perfect explaintion :ro)

I also have a 09 chev cc 2500 and pull a 14000lb 5er....Your comments about what you rig was doing is just like mine while pulling in the mountains...I tow up grades in the northern Rockies and sometimes the tranny gets alittle warmer than normal but cools down very quickly going down the other side..And yes when the fan kicks in you gotta turn up the radio cause its noisy...

Darn David, if i would have known you'd been through this area I would have told you where the good 'locals' spot's are :)
I hope you enjoyed it, you picked a beautiful drive - pretty windy and slow at times( south road pinnacles), but beautiful none-the-less!

Funny thing about the fan, you're going to think I'm crazy but when you're on it and the temperature is rising; let your foot off the accelerator for a second, and the fan will come on earlier than it did for you.
What I've seen on my truck is if i just keep my foot in it the fan comes on itself WOT at about 230.
However, if it's just at 215 or so, it will wait until it climbs to 230 to kick itself on.
If I let up about 215 a bit on the throttle, the fan will come on earlier than 230...
That's why it seemed the truck 'knew' it was on the top of the grade and the fan kicked on - because on top of the grade you weren't in the throttle as much.
Don't get me wrong, if the grade would have lasted longer and you were WOT the entire time the fan WOULD HAVE came on and cooled everything off; just not as soon.
Sounds weird, I know, but it works on mine...

Glad you had a safe trip and enjoy your new truck!!

One reason I installed a deep trans pan on my truck. I used to hit 240 several times a year before the deep pan. Since the deep pan I have never hit 240 its usually 205 on the same grades that used to get me 240. Twice I have hit 215 on a grade when ambient temps were in exccess of 90. Many people say the deep pan won't lower temps which is true in a sense but it will keep high temps lower than they used to be without it. The deep pan will also take longer to get to operating temp which will still help the life of the trans. The cooler you get something to run the longer the life even if its cooler for 20 minutes before reaching operating temp that is helping to extend the life of the trans cumulative over time.