switching t/h mode off and on

[MICKD]

Hey Guys,
Am I doing any damage to the Alli by switching the T/H mode off and on while towing a 6,000#TT? When I start off I use the T/H, when I get on the interstate or highway and get up to speed (over 50-60mph) I switch it off to get the overdrive gear. 3,800 miles on the truck, so far so good. I don,t want to create a problem by doing this. Thanks in advance, Mike smile.gif

[DonG]

Hi,

I have read on this forum that the tow-haul was designed to be used when our trucks are towing 70% of max weight or more. That would be around 10,000 lbs. or above.

I don't think you actually need to use it with your trailer, but using it as you described should not hurt any.

Don

[pinehill]

MIKD.

That's EXACTLY the right way to use your tow/haul mode. You can get into OD a lot quicker that way since tow/haul inhibits the shift to OD until 60+ mph. You can also go into tow/haul when you want to stop or to hold speed on a downhill -- the tow/haul augments braking a lot. Tow/haul will also keep your tranny a lot cooler while negotiating stop and go traffic in town, especially when pulling a load.

[DmaxMaverick]

MICKD

I've been doing that for 56K miles now with my 12K 5'er. No problems that I'm aware of. I don't think it is hurting anything in the least.

IMO, it is a good idea to use T/H mode for starting from a stop and slow traffic. I too use T/H to get up to cruise speed and bump the switch to get into OD. I've towed trailers from about a ton, to 12K the same way.

With T/H off, the torque converter does not lock until about 50 MPH (20 MPH with T/H). Under load, the engine RPM's in a gear, T/C unlocked, is pretty close to one gear lower with T/C locked. I have noticed much better performance and economy this way, as well as minimizing tranny heat generation from the T/C.

Cheers

[MICKD]

Thanks Guys
I didn,t think I was doing any damage but I thought I would check with experts ;) just to be sure smile.gif Thanks again, MICKD