Tow/Haul off or on(ram)

Tow/haul mode keeps the clutch engaged during highway travel. In "normal" mode, the clutch is released whenever you take your foot off the gas (the vehicle "freewheels").

Could this releasing and re-engaging make any difference on wear-and-tear of the clutch when you are pulling a heavy load? I really don't know.

The TC clutch does not release even in normal mode as you slow down until you get down to a certain speed. Tow/haul lowers this speed threshold. The main thing tow/haul does is change shift points. It holds gears longer when up-shifting to keep you higher rpms for more power. This is better for your transmission when towing. It also downshift earlier when decelerating to help slow down the vehicle quicker. This is not good for your transmission, but it is not that bad either.

Another thing that some transmissions do in tow haul mode is increase the line pressure threshold. This changes the shifts from nice smooth shifts to more firm shifts. This is good for your transmission because it decreases clutch wear and creates less heat due to decreasing the amount of time the clutch slips at each engagement/shift.

Regardless of what vehicle you have, I think you should only use tow/haul or OD off modes if you actually see some NEED for that......like the engine is lugging going up small hills.
I would think with an 8 speed transmission it should handle most situations without intervention.

yes, have noticed much firmer shifts in t/h mode

I believe t/h mode also disables the cylinder deactivation but I'm not sure

I read the Owners' Manual for my truck and learned what Chevy had to say about my Tow/Haul system. Basically I engage it whenever I'm towing over 15,000 pounds, which is every time I hook up my trailer (16,500 empty).

I use tow mode and OD off every time I tow.
Less shifting = cooler transmission.

kellem wrote:
I use tow mode and OD off every time I tow.
Less shifting = cooler transmission.

Maybe not.

OD OFF keeps it out of direct final drive.

The torque converter is in constant use and likely will tend to make it run a bit HOTTER.

The act of shifting up and down does not itself generate any more or less heat.

With our 2016 Ram CTD, Aisin, DRW I use T/H when towing much more aggressive use of the exhaust brake! With T/H and exhaust brake on full when slowing a tap of the brake and the exhaust brake and trans will slow you, trans will down shift and brake will stay on until you give it throttle.

I think TH often keeps it out of the highest gear but I still think the computer will let it if conditions warrant; Very flat, no wind, etc.

"but does it do anything at highways speeds on flat roads?"
Depends on the load. If the truck will pull the load in 8th gear then even in tow/haul, it will hit 8th gear.