Transmission Temperature - Tow Haul Mode

My last couple of new trucks have included transmission temp guages. What is considered normal transmission temps, and what is considered to be hot?

I know they put these things on work trucksd to let you know if you are over working your trany when hauling heavy loads, but just how hot is too hot? What is marginal, and what is the best way to cool it down if it does start to climb towards marginal temps?

I suppose this goes hand in hand with the tow/haul mode on these trucks. What exactly does tow/haul mode do?

"Allows you to tow in overdrive," is really a non-specific answer. How? What does it do?

How heavy of a trailer do you need to be towing to justify flipping the trany into tow/haul mode?

I never turn it on for my little couple hundred pound utility trailers, and I always turn it on when towing my boat. Still it would be nice to KNOW what the best thing to do is.

Reply to
Bob La Londe
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Only flip the switch on the 1/2ton when going over a couple thousand lbs or if it seems to 'feel' the load. With the D-Max push the button with the big cooking trailer or when in the hills---haven't hauled a big enuf load it seems for the tranny temp gauge to barely get to the mid point

buzz

Reply to
2fatbbq

I have the 8.1L and Allison tranny in a 2500HD crew cab long box and tow a

32' fifth-wheel w/ a full slide in it. The only time I use Tow/Haul on the truck is in stop and go traffic to keep it from jumping into different gears as quick (a heat builder) and when descending mountains. The tranny braking on the Allison is wonderful!!! There are even times when I have to gas it a bit to keep the speed up where I do want it. Otherwise, the truck is never in Tow/Haul. That engine and tranny just don't require it often. That and the MPGs get beat up even more!!! :-(

I had another 2500HD w/ the 6.0L in it and towed the same fifth-wheel. Had to leave it in Tow/Haul mode on the highway if I was using the AC as it would like to jump around in and out of OD. That or even at times had to leave it in 3.

Tow/Haul basically alters the shift points by letting the gear wind out a bit more, shifts it harder, and prevents the tranny from dropping out of OD as quick as it will w/ it off. No real magic going on. I believe the '03's and up can lock out OD and let you get to 4th gear. That would be nice to have since sometimes OD is just a little to tall. I just play the accelerator pedal to keep it in 4th when it wants to jump around.

Reply to
Kevin

I tow a 35' 5er with an '06 Duramax with Allison transmission and always use the tow/haul mode when towing.

My normal trans temp when towing is just below the halfway mark on the gauge. Sometimes on warm/hot days on long steep grades the trans and engine temp will start creeping up. When it does I turn the a/c compressor off and put the system in 'recirc' to keep circulating the air in the cab. Once I reach the crest, I turn the a/c back on.

As I understand it tow/haul changes the shift points for more rpm before shifts, locks up the torque converter to reduce heat and provides grade braking for down hill. In my opinion, the trucks engine and transmission computers can do a much better job of determining the proper gear for the load and other conditions than the driver can.

My '06 6 speed Allison allows you to select any of the 6 gears as the highest gear to use. Effectively you can 'lock-out' both ODs, drive, 3rd and 2nd.

On the highway my towing is done in the tow/haul mode with the cruise control set. In that configuration the grade braking will come on automatically on down hill when your speed exceeds 4-5 mph over the cruise control setting.

Reply to
Ron Recer

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