Tow mode vs Manual mode (L) on my 6L80 transmission

rav3 · October 2, 2020

I curious as to what the differences between Tow Mode vs Manual Mode on my 2017 Silverado with 5.3l V8. The truck is equipped with the MAX towing package.

I realize that when in (L) manual mode, you can set the highest gear that you want & the transmission will only go to that gear. If I pick 6th gear, how is that difference from just leaving it in drive? Pros verse cons? Does the transmission lockup still take place in 6th gear? Would the lockup happen if I only used the 5th gear option?

With that said, what happens when you leave it in D & push the TOW button? It's my understanding that the shift RPM's/speeds are changed to run higher before the transmission will shift to the next gear. Will it still go to 6th gear? Will the Lockup take place or not? I think the owners manual says that the tow mode will engage a hill decent braking when it senses the down hill condition.

I read where the AFM is disabled when either of these option are picked. Is this correct?

What are the advantages of one mode vs the other?

Can anyone take the time to explain this to me?

Thanks in advanced.

CamGTP · October 2, 2020

Picking 6th gear and leaving it in Drive is no different, it's doing the same thing. The computer locks the torque converter in every gear no matter what mode you have it in, the stock calibration is designed that way on the 6/8 speeds.

You are right on the tow haul, it holds gears longer and will downshift more aggressively to hold speed and for trying to be in the best gear when you get back into the throttle. Grade braking should be enabled with Tow haul mode as well. It will still go into 6th gear but not as quickly and you likely need to be on pretty flat ground. Having it be in 5th gear is probably going to be more common if there are any hills or you are on and off the gas a lot.

AFM is off in M5 and I believe with Tow Haul as well.

sldhead700 · October 3, 2020

I thought I remembered reading some place that when you are in the tow haul mode, that you have to be in automatic not manual mode for the grade braking system to still work?

Sent from my Pixel 4 XL using Tapatalk

redwngr · October 3, 2020

Tow/haul mode raises the shift points, to reduce the amount of shifting back and forth.

It also enables tow/haul grade braking which enhances the way the engine and transmission wok together to help maintain speed when running downhill.

Tow/haul grade braking does not come on if the trans is in manual mode.

sldhead700 · October 3, 2020

Tow/haul mode raises the shift points, to reduce the amount of shifting back and forth.

It also enables tow/haul grade braking which enhances the way the engine and transmission wok together to help maintain speed when running downhill.
Tow/haul grade braking does not come on if the trans is in manual mode.

That's what I thought.

Sent from my Pixel 4 XL using Tapatalk

brokesilverado · October 4, 2020

You can also push the tow haul button in for 5 seconds or so & turn off the grade braking.

M1ck3y · October 4, 2020

Any difference with regards to timing or transmissions programming? I'm curious about the stuff that's not in the owners manual.

JimCost2014 · October 4, 2020

Tow/Haul Mode Vehicles with an automatic transmission have a Tow/Haul Mode. The Tow/Haul Mode adjusts the transmission shift pattern to reduce shift cycling. This provides increased performance, vehicle control, and enhanced transmission and engine cooling when driving down steep hills or mountain grades, towing, or hauling heavy loads. The selector button is on the end of the shift lever. Turn the Tow/Haul Mode on and off by pressing the button. When the Tow/Haul Mode is enabled, a light on the instrument cluster will come on. See Tow/Haul Mode Light 0 146 and Hill and Mountain Roads 0 269. Also see “Tow/Haul Mode” under Towing Equipment 0 345. Tow/Haul Mode Grade Braking Tow/Haul Mode Grade Braking is only enabled while the Tow/Haul Mode is selected and the vehicle is not in the Range Selection Mode. See “Tow/Haul Mode” listed previously and Manual Mode 0 292. Tow/Haul Mode Grade Braking assists in maintaining desired vehicle speeds when driving on downhill grades by using the engine and transmission to slow the vehicle. On vehicles with a gasoline engine, to disable or enable Tow/Haul Grade Braking within the current ignition key cycle, press and hold the Tow/Haul button for five seconds. When the button is released, the requested mode change is made. A DIC message is displayed. See Transmission Messages 0 162. On vehicles with a diesel engine, Tow/Haul Mode Grade Braking can be enabled or disabled by pressing the Tow/Haul Mode button. Use the exhaust brake and Tow/Haul Mode for maximum grade braking. See Towing Equipment 0 345. For other forms of grade braking, see Automatic Transmission 0 289 and Cruise Control 0 311.

swathdiver · October 4, 2020

There's no benefit to Tow/Haul mode unless you are at or above 75% of your GCWR. So if your GCWR rating is 14,000 pounds, the truck and trailer ought to weigh more than 10,500 pounds to realize the benefits. I can attest to this, trans feels funny if used with no or just an empty little trailer, operates and feels great with a full load.

CamGTP · October 4, 2020

Timing and fueling does not change with tow haul mode. There aren't separate tables for when that button is pushed.

I will say this though, timing can be reduced if knock is detected by the knock sensor. Hauling a heavy trailer puts more load on everything and the engine works harder. Lower octane fuel could be more prone to knock if cylinder temps and overall engine temps get really warm.