OVERDRIVE or NOT

[Billy Bob]

How many of you tow your PU in Overdrive or take it out of overdrive.

I have towed my boat with 3 different TV's in the last 21 years and have kept it in overdrive, but my PU is much heavier so I am thinking of locking out overdrive while towing the PU. I'm sure gas mileage will suffer big time but I don't want to over heat the tranny.

[tlhdoc]

IF the TV doesn't shift in and out of overdrive I tow in overdrive.  If we are in a mountainous area with ups and downs I don't use overdrive.

[flyfisherman]

So much depends on just what your tow vehicle is and how it's set-up.

I tow with a full size GMC pick'em up and I can, of course, on level highway just cruise right along in O/D. Once I get to the rolling hill country, the truck has a transmission "tow/haul mode" which I select but still leave in O/D - this can hold gears longer to transfere more torque when needed. But when I reach the mountains, for sure, I drop the selector into 3rd gear and leave it there. Not only better on climbing mountain passes but also holds things back on the trip down with better control and less wear on the brakes.


Fly

[brainpause]

I have a manual five speed.

Having said that, when climbing hills, or when I'm shifting often, I just cruise along in fourth gear sometimes. Gas mileage MAY suffer some, but it might not. If your engine is struggling to keep speed, it does try to increase RPM's (with extra fuel). Sometimes that struggle isn't too successful, especially with my four cylinder truck. So, by keeping it in a lower gear for hills and such, I'm actually probably helping out the drivetrain.

I said all that to say this: Pay attention to the gear your vehicle has selected. If it hunts once or twice, go ahead and lock out OD. Don't be afraid to drive in 3rd (or 4th, as the case may be).

Larry

[SpeakEasy]

Here's the way I look at it:

The manufacturer tells me to lock out O/D while towing.
On a 3,000 mile camping trip last summer, I averaged 16.4 MPG.
If I could get my mileage up a couple MPG by using O/D, that would have saved me less than $50 in gas costs on that trip. The extra $50 I spent on gas by locking out O/D is relatively cheap insurance, and it is what the car manufacturer recommends. That's why I don't use O/D when I'm towing.


It does tempt me, however, when the engine is running at a higher RPM for hour after hour. I want to reach down and flip off that switch to let her go into O/D.

[cyclone]

Not.  The owners' manual says don't; we listen.

[wavery]

As stated before, it's not worth using the OD IF you maintain 55MPH. At 55, you are really not turning enough RPM to justify using OD. That is why the manufs recommend not using it, they assume that you will not be exceeding 55MPH.

However, if you tow at 65MPH on flat roads (which is also not recommended), it may be worthwhile to use the OD. to keep the RPM down & increase fuel economy. The key is to remember to take it out of OD when you get un-level terrain or drive below 55.

As stated earlier, the TV will let you know if you shouldn't be using OD. You will notice it shifting too often.

BTW........NEVER leave it in OD going down-hill.

[tlhdoc]

they assume that you will not be exceeding 55MPH.

Who is the "they" that is  are saying, assuming you will not be driving over 55 mph?  The speed limit on most interstates is 65 mph or faster.  There is nothing in my owners manual that says to tow at 55 mph or slower.
 

However, if you tow at 65MPH on flat roads (which is also not recommended)

Who doesn't recomend it and/or where are you getting this towing information from?
 

BTW........NEVER leave it in OD going down-hill.

Again I ask why?  I know on a steep down hill not to use overdrive, but I do it all the time on a 20 mile gradual down hill that I tow on.  I have to give the TV gas, so why shouldn't I tow in overdrive, please explain.

[abbear]

Who is the "they" that is  are saying, assuming you will not be driving over 55 mph?  The speed limit on most interstates is 65 mph or faster.  There is nothing in my owners manual that says to tow at 55 mph or slower.
 
 
Who doesn't recomend it and/or where are you getting this towing information from?

For Wavery and myself the "they" would be the California Highway Patrol.  In CA cars towing trailers are limited to 55 mph.

[wavery]

Who is the "they" that is  are saying, assuming you will not be driving over 55 mph?  The speed limit on most interstates is 65 mph or faster.  There is nothing in my owners manual that says to tow at 55 mph or slower.
 
 
Who doesn't recomend it and/or where are you getting this towing information from?
 
 
Again I ask why?  I know on a steep down hill not to use overdrive, but I do it all the time on a 20 mile gradual down hill that I tow on.  I have to give the TV gas, so why shouldn't I tow in overdrive, please explain.

Ya......sometimes I forget that this is the WWW. :p Ca is 55. I may be wrong but I thought that most states had a 55MPH limit for vehicles towing a trailer :confused: .

The comment about hills, I thought, was obvious. Evidently I was wrong . To clerify.........If you are on a downhill run that your vehicle may require braking, OD should not be used. When the vehicle is in OD, it has little to no braking capacity. When the OD is disengaged, the engine will help control your downhill speed and thus reduce the need for braking and help keep the brakes from over heating. Brake fade is extremely dangerous (as we all know) and it can occur before you are even aware of it. Once brake fade occurs, it is nearly impossible to bring a vehicle to a stop. Brake fade is the most dangerous element in towing.

I (personally) would not consider "a 20 mile gradual down hill that I tow on. I have to give the TV gas" as "down-hill"........again, that may be my California mentality coming through :p . I would consider "Down-hill" as driving on a road that the vehicle must be slowed by braking, even if only slightly or intermittently.

[brainpause]

I believe wavery is talking about a hill that is much more of a downgrade. As he said, one that requires either constant or occasional braking.

We have a large hill (we call it the mountain) that is a couple of miles over, and we travel it often. It is a 9% grade, and, towing or not, I am always in 4th gear, sometimes 3rd coming down, NEVER fifth (my overdrive), or I'd fly down it, and there are sharp curves at the bottom!

Larry

[tlhdoc]

When the vehicle is in OD, it has little to no braking capacity.

I don't believe this.  I don't believe that OD has any effect on the vehicle brakes.  The rest of what you said is correct, that the engine in a lower gear will keep the vehicle from going as fast, BUT no matter what gear you are in your brakes are an independent item, towing or not.  In OD your vehicle still has breaking capacity or people flying down the freeway at 80 mph in overdrive would not be able to stop their cars.  The faster you go towing or not the longer it takes to stop.

[dthurk]

I don't believe this.  I don't believe that OD has any effect on the vehicle brakes.  The rest of what you said is correct, that the engine in a lower gear will keep the vehicle from going as fast, BUT no matter what gear you are in your brakes are an independent item, towing or not.  In OD your vehicle still has breaking capacity or people flying down the freeway at 80 mph in overdrive would not be able to stop their cars.  The faster you go towing or not the longer it takes to stop.

I think wavery's talking about engine braking here.  The lower the gear the vehicle is in, the slower the vehicle will descend on it's own without using the brake pedal, reducing the possibility of brake fade.  In overdrive, the vehicle would almost be free-wheeling down hills, requiring use of the brake pedal more than necessary to slow or stop the vehicle.  This obviously depends on the grade and length of the hill in question.

It appears you're both right, but one's talking apples and the other's talking oranges.

[Civil_War_Buff]

My owners manual states that when the transmission starts "searching" which I take to mean upshifting and down shifting erratically, then take the transmission out of OD.

Also, a "rule" passed on to me from a family member who was a long haul truck driver about coming down hill while towing is...."use the same gear coming down that you used going up".  It made sense to me when I heard it, and I follow that advice quite successfully today.

My .02

[wavery]

I think wavery's talking about engine braking here.  The lower the gear the vehicle is in, the slower the vehicle will descend on it's own without using the brake pedal, reducing the possibility of brake fade.  In overdrive, the vehicle would almost be free-wheeling down hills, requiring use of the brake pedal more than necessary to slow or stop the vehicle.  This obviously depends on the grade and length of the hill in question.

It appears you're both right, but one's talking apples and the other's talking oranges.

That's correct. I seem to be having a problem explaining things here :eyecrazy: . I sometimes assume a certain amount of mechanical or physics knowledge and that is not a fair assumption. I can see how my comment, "When the vehicle is in OD, it has little to no braking capacity." could be mis-understood. The IT that I was referring to was the vehicle's engine. That may have been better stated "When the vehicle is in OD, the engine has little to no braking capacity". You see, the vehicle must be viewed as a mechanical device that works as a cohesive unit but demands some human management of it's separate components...IE the gas pedal, brake pedal, cruise control and transmission controls. It is dangerous to assume that the vehicle is capable of managing all of these components under every situation. The driver must (IMHO) take a certain amount of responsibility to over-ride the vehicles automated systems. Towing is one of those situations (IMHO).

There are several ways to "Brake" a vehicle besides stepping on the brake pedal. You can "Gear down", you can pull the emergency brake, you can run the vehicle onto the soft shoulder or (in the case of brake fade) you can use a "Runaway truck ramp" or in extreme cases you can run the vehicle into something to slow it down or stop it to avoid a runaway collision. All of these are "Braking" the forward movement of the vehicle.

So that there is no further mis-understanding here.......when driving on hills it is best to drive in the highest gear that you can without having to over-use the vehicles brakes. Once you have to start braking to keep the vehicle from  accelerating (through gravity) down a hill, it is time to start gearing down by taking the TV out of OD.

OD is the highest gear that your vehicle can achieve. Taking the vehicle out of overdrive is the first step in "Gearing down". The purpose for "gearing down" is to use the back pressure of the engine to provide "Braking" power. OD gear has the least amount of braking power from the engine. On steeper hills, it is sometimes necessary to put the TV into 3rd or 2nd gear to avoid the over use of the brakes in mountain driving. The lower the gear, the more resistance that is applied by the deceleration of the engine.

Large diesel trucks actually have a device to increase the back-pressure in the engine to avoid using the brakes. It's sometimes referred to as "Engine brakes". Professional truck drivers know that using the brakes is a last resort measure and MUST not be over used when hauling a load.

This train of thought, "I don't believe this. I don't believe that OD has any effect on the vehicle brakes." is really scary. It is critical to understand that the engine and transmission are a tool to avoid brake fade. Driving in the hills with the OD engaged while towing is inviting disaster. The subtle use of the vehicles brakes generate a tremendous amount of heat. Anything that you can do to avoid having to use the vehicles brakes and keeping the brakes cool for an emergency is essential in towing. Taking the vehicle out of OD is step #1.

It is almost impossible to recover from brake fade, once it occurs in a downhill situation. If anyone here has ever experienced brake fade, your story and feelings may be beneficial to this discussion.