OK to use cruise control while towing?

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By Russ and Tiña De Maris
When towing a travel trailer, can you use the cruise control? What about an overdrive transmission? These are questions that can puzzle new RVers — and even some veterans.

First, let’s talk about cruise control. Here’s a school of thought where most folks who’ve had cruise tend to agree: Towing a trailer with cruise control is fine — with certain caveats. Towing “on the flat” is a snap, and may save you fuel if your cruise control handles the accelerator. However, if you encounter a situation where your transmission begins to “hunt,” that is, to move from one gear to another and back, then you may need to make a change. Usually the “hunting” can be stopped by simply slowing down or speeding up just a tad. If this settles the transmission down, well and good. If not, you may be back to “flying manually.”


Cruise on hills can be a different story. We’ve found by our own experience that leaving the cruise control engaged when hill climbing is OK when the grade isn’t real steep. On steeper grades the cruise will try and maintain speed, downshifting, and eating more fuel. If you have a fuel economy gauge in your rig, try using the cruise while hill climbing and see what happens to consumption. We often tow up hills by with the cruise “off” and holding the accelerator at a given point–this means slowing down, of course, and down shifting where needed, but it pays at the pump.

On the downhill side, safety is the chief concern. Cruise control won’t hold your speed from going “over” the set-point, so on a steep downgrade we feel more comfortable with the cruise off.

Other places to forgo the comfort of cruise control include icy or otherwise slick roads, and in heavy traffic. We’ve found some bridge decks set up an awful “bounce” for our truck and trailer combination that’s enough to rattle your teeth out. Drop off the speed control and slow down to get these nasty bounces under control.

FOR AUTOMATIC TRANSMISSION USERS, what about overdrive while towing? There were some trucks produced in the past that decidedly recommended against towing in overdrive. This is because by the design of these transmissions overheating could be a problem. Towing adds a heat load, and to keep the transmission cool, fluid is pumped through a radiator-like device to cool it off. In overdrive, some transmissions couldn’t pump it fast enough to handle the added heat load, and the results could be really expensive.

First rule: Read your rig’s owner’s manual. If the manual rules out towing in overdrive, then lock out the overdrive. If the manual allows towing in overdrive, you could be conservative and safe by installing a transmission temperature gauge and keeping a close eye on it.

Finally, you may have a rig with a “Tow/Haul” switch. For many transmissions, that switch resets the shift points of your transmission to a selection more appropriate for the extra transmission load. It may also lock up the torque converter (reducing heat build up), and may even lock-out overdrive. Again, check your owner’s manual to be safe.

#nrv;##RVT928

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Michael Druck

On Cruise Control and going down hill you said: “On the downhill side… Cruise control won’t hold your speed from going “over” the set-point, so on a steep downgrade we feel more comfortable with the cruise off.”

You are right about using Cruise Control on downhills up to a point. “Steep downgrades” – and I’d add rainy days – are not a good time to use Cruise Control on downgrades or corners.

Having said that – using Cruise Control on moderate downgrades can depend on the tow vehicle. Our 2015 RAM 2500 Tradesman (6.7 Cummin’s Diesel) DOES auto-downshift if our speed exceeds the Cruise set point by 4 to 5 MPH – and it will shift down several steps if the first doesn’t start slowing things down.

In addition having an Engine (“Jake-” or “Exhaust-” ) Brake set to ON provides up to 275 HP of ‘braking’ which does wonders on downhills providing no-white-knuckle control and minimal brake wear on both the truck and trailer.

Note that this RAM’s Engine Brake has two settings – only engages when the brake peddle is depressed, or anytime you let off the the accelerator above 55 mph (or around 1500 RPM) in from Overdrive through 3rd (6 speed auto).

ThreeQuarterTon

Most owners manuals recommend shutting off cruise control when driving on WET or icy/snowy surfaces! I always do,whether towing or just driving the Malibu or the Jetta!
Some years ago, had a gust of wind put the 36′ motorhome I was driving at a 45+ degree angle to the highway , if cruise been on I probably would not be here to tell about it!!
Nearly had extra laundry that day!

Al F

Many times on long uphill grinds in the mountains at 30-45mph, I’ll manually put the transmission in 2nd or 3rd gear and then set the cruise control. This lets me sit back & relax for the next 2 to 4 miles.

John T

In my Ram 1500, there is a setting accessible through the dash display menu to prevent the transmission shifting in cruise control unless the speed changes by 5 mph. That prevents all hunting. Look for it in the owners manual.

Ed D.

I had a 2002 Nissan X-terra that was always on overdrive. I couldn’t turn the overdrive off. So, I had a hell of a time towing a travel trailer uphill through the Rockies. I was lucky if I could go 40 mph.

Bill Dornbush

My 2014 Jeep Grand Cherokee with V-6 and 8 speed transmission does reduce the speed on downhill slopes. When the speed exceeds about 5 MPH over the speed set, the transmission downshifts to a lower gear so that engine braking will start happening. Often, this is enough to slow us down. Sometimes, the slope is too steep for engine braking alone to slow us enough, and then I press the brake, which disengages the cruise control, but the transmission continues to apply engine braking. It is a rather “smart” transmission and will sometimes shift to a lower gear to slow us down even when cruise control is not engaged.

John Koenig

I’m in my second RV. The first was a 17′, 2010 Casita Spirit Deluxe Travel Trailer (which was an EXCELLENT way to “test the waters re RV living without spending a fortune). After 50,000+ miles over four+ years, I “graduated” to a TRUE Super-C motorhome (a 2015 Dynamax DX3-37RB) which is built on a Class 7 HDT (Heavy Duty Truck) cab/chassis with a 9L Cummins ISL9 350HP diesel puller engine. I use cruise control whenever I’m on a limited access road. My Super-C doesn’t even know that it’s pulling a 25′ Featherlite car trailer! I recently upgraded the rear camera. The new camera has a wider field of view, pan and tilt and, connects to a dedicated 8″ monitor that allows me to see everything that’s going on behind me in real time. I’ll be hooking up a Silverlight engine monitoring system soon. That will provide, in real time, exactly what’s going on with my coach. I’ll get the information that will allow me to test, on the fly, how changes in my driving can effect fuel economy. When it works right, technology can be amazing!

Wolfe

Although I generally agree with the article, several notes based on my RAM at least…
1) cruise locks out overdrive. No reason since tranny is cool and OD works driving by foot.
2) T/H locks out overdrive. No reason since tranny is cool.
3) cruise locks out MDS (partial engine shutdown). MDS works less towing but still works (by foot), so not sure if there is a reason but it’s dramatic at the pump.
4) cruise does use engine braking including downshifting. But I’m better at it.

The above combinations take > towing < mileage from 15-17 with my foot, down to 8-10 (and diving in hills)… I will set CC on dead flat highway just to remind myself how bad it is, but my high-teen tow mileage results from manually:
A) holding steady RPM and letting tranny shift
B) pulsing the gas to "kick-shift" my auto manually and to maximize MDS active time.
C) Dont speed. Really. It's a house.

Donald N Wright

I have an F-150 turbo/ten speed pulling Aliner Range Popup. Ford service department advised me not to bother with “tow/haul” as it is a popup. second, cruise control perfect on flat highways, off cities, hills, or heavy traffic. Let the transmission choose what gear it needs to be in. Oh, have fun !

John M

I find that my 2011 2500HD Chevy does a better job down hill letting the cruise control balance the gears and the exhaust brake to hold the speed down. I will usually reduce the speed setting to limit the top speed where I need it and the cruise (in Tow-Haul mode) manage it.

Dave W

I seldom use cruise when towing unless my skiing destroyed knee acts up. The fuel milege suffers as well, trying to maintain speed in the mountains or even rolling hills. If the road is virtually dead flat interstate, yes, I may then use it. With no trailer hooked on, it’s used as much as possible.

David Ozanne

My transmission holds the speed down in cruise. I think that many of the newer ones do this.

Wayne

Some older trucks like for example 06 Rams the stock electric engine fan does not kick in when the tranny temp rises. Only when coolant rises. Many a tranny has been destroyed from heat build up that the driver is unaware of.
This can be prevented by adding a pair (in my case) of electric fans that are triggered on by the temp of the transmission.
In these trucks even in cold temps if you towed up a steep hill even down in 2nd gear for just a few minutes the temp soars. A gauge set is a must.

J. G.

Your information is not entirely accurate. I know that some of the newer pickups will automatically engage the engine brake (may call it exhaust brake or something else) when going downhill using the cruise control. Will it always work on all hills, probably not on the steepest but it works in most cases. Of course the driver needs to understand that all the controls have to be set properly to cause this to happen. So read your manual!