Flat Tow

Weedguy · May 22, 2022

Is anyone flat towing a 2500 diesel behind a motorhome or more specifically could tell me who a good resource person for this would be?

MTU Alum · May 22, 2022

Here are the steps, they are also in your owner's manual. You can only flat

1. Put transmisson in neutral and then shift trans

MTU Alum · May 22, 2022

Just now, MTU Alum said:

Here are the steps, they are also in your owner's manual. You can only flat tow 4wd trucks. Transfer case must be in neutral and transmission in park.

1. Put transmisson in neutral and then shift transfer case to neutral.

2. Put transmission in Park

3. Disconnect all batteries.

sheath · May 22, 2022

36 minutes ago, MTU Alum said:

Do you understand the reasoning behind disconnecting the batteries?

Reason I ask is one of the most common units for a "toad" (vehicle towed behind motorhome) is a Brake Buddy. This style of unit applies braking force through the toad vehicle brake system by activating the brake pedal, which would normally activate the vehicles brake lights. It is powered by the toads battery system.

They do offer a kit to connect directly to the vehicles battery. So a work around would be to use that kit, and also a separate tow light system. But it is clunky compared to tying into the vehicles lighting system.

Weedguy · May 22, 2022

Thank you. I am aware of the steps. The last post gets more to the root of my question. Want to tow with an Air Force One brake system that requires power. Therefore I have to disconnect the batteries but get power to the AF One and the lights. Looking for help on the steps to do that or to put the installer in touch with. We have been pulling a Jeep Eco Diesel which is a piece of cake. I can’t drive the dam thing. We decided to tow pickup and wife hates my Super Duty and the fact I ordered a new one. To keep the peace we went back to GMC (we have had a bunch of them). I like it OK but wondering if got myself in a can of worms towing this thing.

MTU Alum · May 22, 2022

The wheels moving will cause serial data bus to wakeup and this could cause modules to start to activate things. Best case serenrio your battery is dead at arrival. We have seen melted brakes, fires, etc. I know of at least three broken 10 sp cases of people not following the directions as they exist now.

#iworkforGM

MTU Alum · May 22, 2022

You probably have to talk to dealer and see if they would open a TAC case on it. There probably is a series of fuses that could be pulled but its, easier for us to disconnect battery.

#iworkforGM

sheath · May 22, 2022

Thanks @MTU Alum This makes perfect sense.

TAC case through dealer is a great idea. I'm guessing it won't be the first request.

Weedguy · May 22, 2022

My dealer had a blank stare

nards444 · May 23, 2022

Curious as to what the details are on this? Seems like if this isnt a one off thing you tow a small car like most I have seen.

sheath · May 24, 2022

When hunting out of state, I pulled a 3/4 ton Dodge 4x4. The class A was base camp, and the Dodge worked as a field camp.

My brother had the perfect setup. Dodge Power Wagon w/popup camper that he also pulled with a class A.

Starting to see more Class A pulling Jeep Gladiators set up for overlanding.

swathdiver · May 24, 2022

Saw a Class A towing a 3500 with an eight foot bed yesterday. The manual says to put the transfer case in neutral and let her rip. Doesn't say anything about disconnecting the battery that I recall.

Edited May 24, 2022 by swathdiver

redwngr · May 29, 2022

Dinghy towing instructions depend on the year of the truck.

OP's avatar says he has a 2022 Denali HD

Yes, the current 2500/3500 OM does call for battery disconnection.

Electric parking brake on a keyless access truck is one reason to disconnect the battery?

From 2022 2500/3500 OM

Dinghy Towing (Two-Wheel-Drive Vehicles and Vehicles with a Single-Speed Transfer Case)
Caution
If a vehicle with two-wheel drive or a single-speed transfer case is towed with all four wheels on the ground, the drivetrain components could be damaged.

The repairs would not be covered by the vehicle warranty.

Two-wheel-drive vehicles and vehicles with a single-speed transfer case should not be towed with all four wheels on the ground.

Dinghy Towing (Vehicles with a Two-Speed Transfer Case)

Only dinghy tow four-wheel-drive vehicles with a two-speed transfer case that have an N (Neutral) and a 4 n (Four-Wheel Drive Low) setting.
{Warning
Shifting a four-wheel-drive vehicle's transfer case into N (Neutral) can allow
the vehicle to move even if the transmission is in P (Park). You or others could be injured. Set the parking brake and use wheel blocks before shifting the transfer case to N (Neutral).

To dinghy tow:

1. Position the vehicle being towed behind the tow vehicle, facing forward and on a level surface.

2. Securely attach the vehicle being towed to the tow vehicle.

3. Apply the parking brake and start the engine.

4. Shift the transfer case to N (Neutral).

See “Shifting into N (Neutral)” under Four-Wheel Drive 0 240.

5. With the engine running, release the parking brake and verify that the transfer case is in N (Neutral) by shifting the transmission to D (Drive) and then to R (Reverse). There should be no movement while shifting the transmission.

6. Shift the transmission to D (Drive).

7. If equipped with an ignition key, turn the ignition to ACC/ACCESSORY.

If equipped with Keyless Access, turn the engine off. Disregard the Shift to P (Park) DIC message. See Ignition Positions
(Keyless Access) pg 229 or Ignition Positions (Key Access) pg 227.

To avoid death, serious injury, or property damage, before dinghy towing the vehicle, always disconnect and
secure the negative battery cable and cover the negative battery post and cable with a non-conductive material. If the
battery is left connected or the battery cable contacts the post, the Electric Parking Brake may activate during towing, which could cause a crash.

8. Disconnect the negative (–) battery cable. See “Negative Battery Cable Disconnection” in Battery - North America pg 324.

9. Shift the transmission to P (Park).

10. Move the steering wheel to make sure the steering column is unlocked.

11. If the vehicle has an ignition key, keep it in the towed vehicle in ACC/ACCESSORY to prevent the steering column from locking. If the vehicle is equipped with Keyless Access, keep the RKE transmitter outside of the vehicle and manually lock the doors.

Access the vehicle by using the key in the door lock. See Door Locks pg 21.

@Weedguy

All this info should be in the OM that should have come with the truck.

If you didn't get one, or if you prefer to have a electronic copy ( pdf ) they can be downloaded free from GM's websites.

Afaik, all the 2020+ HD Denali will always be 4wd and have a 2 speed transfer case suitable for flat (dinghy) towing.

Edited May 29, 2022 by redwngr

Tspoon 2024 2500 HD 6.6L · July 24, 2024

I have a 2024 Chevy 2500 HD that I plan to flat tow. I see in the owner's manual that you must disconnect the battery during the flat tow set-up process. My question is has anyone install a battery disconnect switch on the negative side of the battery to prevent you from having to disconnect the battery from the battery post every time you flat tow? Thanks in advance.