So I've got three 6.0s in the fleet, and they all have torqshift transmissions with the tow/haul button. The ambulances are monstrously heavy -- typically 12,000 to 13,000 pounds each.

As far as the drivetrain is concerned, it is towing an 8,000 pound trailer all day every day.

We don't have problems with transmissions overheating, but I wonder what the torqshift experts here think? Would you keep the vehicle in tow/haul mode all the time? Why or why not?

 

It won't hurt it if you don't use it, but I like the overall performance of the truck with it engaged when towing medium to heavy weight.

 

I think you would be ok either way but I would use it. Engine braking and earlier downshifts when coming to a stop in traffic works well, saves the brakes and just feels right. Later up shifts when accelerating keeps the engine in the power band a little better. I'm a little lighter than you and just about reversed in weight 8k truck 10k trailer. I like tow-haul a lot but I do sometimes turn it off at highway speeds on level ground because it often drops down a gear on low short hills that the tuck pulls easily without the downshift.

 

You won't hurt anything by using it or not using it. The system is designed to live either way.

 

I am a firefighter and we have a group of these in rotation. I can tell you when it down shifts it is not smooth in the back. Your patient (especially if the are on a backboard or if they have broken limbs) will appreciate it out of tow/haul. Not to mention the techs in back. Every time it down shifts they will get lurched forward. If it doesn't matter mechanically, i say keep it off.

 

I agree. Been there done that. Keep it off when people are in the back.

 

FWIW a normal empty F350 weighs around 8K, so with a 12K ambulance it's more like a 4K trailer. When I tow my car hauler empty, it weighs 4K and is a box bigger than a typical ambulance in cross-section. I find that I like NOT using tow haul in that situation - it stays in 4th gear too long around 55 mph, it down-shifts aggressively when coming to a stop, and the truck handles that load actually pretty easily. Where I do use it often is selectively when coasting down hills where it adds engine braking that can be nice. It still down-shifts pretty aggressively if you had someone working in the back.

Brian

 

Mark... New to diesels and the latest technology here. My old '90 F250 gasser had the overdrive button which only disabled 4th gear when towing my boat...

From your comments; and those of others, can I assume that when towing my 10K 5'er, that the Tow Haul (that I have) only changes the shifting patterns of the transmission; but keeps all gears available?

Jim

 

It changes the shifting pattern and gives you a kind of engine brake by using the turbo as an exhaust brake of sorts. It doesn't lock out any gears, and by 60 mph you are in fifth for cruising.

Brian

 

It also changes the aggressiveness of those gear changes - making them shift faster (and consequently feeling rougher.)

 

I always wondered if it did change the shift speed (like an old-school shift kit would) or if it just felt harsher because it was at a higher rpm. Anyway, I used to use tow-haul all the time I was towing, but I stopped except for when I wanted the engine brake thing. Usually I like to roll down hills free to get better fuel mileage. With my trailer I get enough aero-drag braking that I can roll down a 6% grade and barely pick up any speed...


Brian

 

I didn't like the tow/haul much with my old truck either. And that was 9900 pounds of service body and towing a 7000 pound trailer frequently.

Josh

 

If I understand correctly, tow/haul isn't just a set of fixed parameters. It learns and changes strategy a little the more you use it.

 

Yes, that's right. All the gears are used, the shifts are at higher speeds.
Nope, not true. The nominal shift time that we were shooting for for ALL shifts is 0.400 seconds. Tow/haul on or off.

You don't understand correctly. It does not learn and change strategy. It does learn how long each shift takes from when the computer commands the shift until it measures the shift ended from data from the speed sensors. Then it adjusts the pressure for the next time it makes that shift to keep each shift as close to the ideal 0.400 second shift time.