Hi all, I just got a 2003 GMC 2500HD Crew Cab and the day i got the truck i hooked up the trailer and hit the road. I know probably not a good thing but my 94 GMC gasser gave up the ghost on the way to the camp ground and i had already lost one night of preciouse camping time
so as i was towing with the 2003 i was wondering the following:
When towing my '85 23 foot travel trailer (about 3300 lbs) should i use tow haul?
should i lock out Over drive?
is it ok to tow with over drive activated?

My '94 gasser STRONGLY recommended never to tow in Over drive.

I would not lockout OD unless you get to a place where the tranny is downshifting and up shifting repeatedly. Small hills at 55-60 seem to confuse the tranny, especially when on the cruise.

I regularly pull a 6000 lb utility trailer in overdrive and have pulled a 8500lb trailer in overdrive. 3500 lbs won't even break a sweat with a duramax. You may find an occasional long steep hill where it will kick down. I don't even need to use tow/haul unless I am coming DOWN a steep grade.

I don't tow as heavy as some of the guys on this forum, but I tow frequently. I usually put it in tow/haul, but never lock out the overdrive. The D-Max never breaks a sweat.

I tow a boat (4500lbs) first two trips I got 12mpg in tow/haul mode. I was talking to the dealer and was told to not use the tow/haul mode to see if I get better gas mileage. Guess what I got 17.5mpg without tow/haul mode, huge difference. I knew I got 14.5mpg towing my 12500lb fifth-wheel so I new something was wrong. Funny how well tow/haul works on a heavy load but not on a light load. Just FYI.

Rgds,
J:cool2:

Towing a 5000Lb trailer behind an 01 C2500HD, 8.1, Allison, 4.10....
is it okay to tow in OD, with occasional T/H as needed?

The key point here is ALLISON...an actual TRUCK transmission......the FIRST automatic to ever belong in a truck.:rant:
All previous automatics cannot hold the full engine power in OD, hence the need for a lockout and there uselessness in a truck. The OD lockout was only added (in 03 IIRC) to the Allison because of the mindset created by previous (junk) auto trannies. The only need for the lockout is for big programs and near GCVW loads.
I only use T/H for loaded down hills and for 30-40 mph winding canyon roads. (Lower transmission temperatures due to locked torque converter in T/H)
If it wasn't an Allison, I'd still be shifting my own gears.

Hey Boondokr....does that mean I should keep it in OD most of the time...unless terrain
warrants a lower gear? I don't have the lock out on my 01.

I tow 4 dairy heifers(and cows at times),about 9k total, along with all required show stuff all over and only use T/H in towns, keeps convertor locked and temps down a bit, this with a 8.1.

Just got back from a 3450 mile trip, towing my 5'er (almost 12,000 #)on I-81 in the hills of VA and Wva...kept the O/D on at all times with no problems....she ran really good....nice to have that allison in there....shifted when it had to and no real problems at all....diesel was expensive in the south up to 3.59/gal....good luck