tow in overdrive

I just bought a pop-up trailer (1700 lbs dry weight, probably 2200 - 2400 loaded with gear). Then I bought a 2003 SportTrac to tow it. It came with a receiver hitch on it. I towed it recently (unloaded to service center to get some work done on trailer) on fairly flat ground and then on the way home, through some hills. On flat ground with overdrive off it ran around 3200 RPM's and really seemed like it wanted to go to overdrive. I turned OD on and it towed fine (2100 RPM’s), only once slipping down into 4th on a slight incline. Through the hills I kept the OD off and it still ran around 3200 RPM but had more power pulling up the hills. My question is can I tow in OD on flat ground?

 

[jimbo74]

i wouldnt....

 

[cabennet]

why not

why not?

 

[JDraper]

First thing I would do is add an extra tranny cooler to the front of the vehicle, even if it already has one. The transmissions in the V-6 Explorers is one of the weakest points in the vehicle. Temperature is the enemy.

Having said that, I have towed quite a bit with various Explorers, and I am constantly flipping it in and out of overdrive. I do use overdrive on the flats and downhills, but generally turn it off manually on uphills.

 

[robeyster]

I just recently started towing with my explorer and my father in law is a mechanic at the local ford dealership. He has told me to always keep overdrive off while towing he said it is really bad for the transmission it gets really hot. He has always said it is cheaper to spend the extra gas money then to spend money on the transmission.

 

[cabennet]

I'm sure that I have a tranny cooler as well. Does that change anybody's opinions?

 

[MountaineerGreen]

On flat ground, I sometimes tow in OD, especially with a lighter trailer. In the hills, never never. Like others said, the trans is the weakest link, you certainly don't want to risk it over a few gallons of gas. I'd think about a temperature sensor so you can really see what is going on as you tow.

 

[Anime]

In general, it's a bad idea to tow in overdrive, but really it depends on the rear end gearing, and what's being towed. With 4.10 gears and a light load, towing a light, flat trailer in overdrive is no problem. Towing a big box trailer with lots of wind drag though, even if it tows in overdrive, it will get that tranny real toasty. So, check the rear end gearing, and if the trailer is pretty flat, well below the tailgate, and the road is VERY flat, sure. If it's got higher gears, or the trailer is boxy enough it sticks up higher than the bed or is wider than the truck, or if theres hills, it's probably not worth it. Better to just turn overdrive off, slow down, and change the tranny fluid at regular intervals to keep things working smooth.

 

[JDraper]

I'm sure that I have a tranny cooler as well. Does that change anybody's opinions?

Nope..add another one...excessive heat will KILL your transmission and the factory cooler is just barely adequate without towing anything (even with the towing package...)

 

[cabennet]

confused

Ok I am a little confused, not being much of a mechanical person. I thought that excessive shifting of gears is what heated the transmission up. If I am just towing in OD with no gear hunting, then I don't understand the problem. It's not just the fuel economy I am concerned about, the truck really felt better to drive in OD. It just did not sound good and really felt like it wanted to shift into OD when I had it off.

 

[gijoecam]

In general, on flat ground, if it'll hold OD on the minor hills, leave it there. You won't be hurting a thing. However, the minute it starts hunting, or you find yourself approaching the hills, turn it off, just like you did. Perform regular fluid and filter changes every 30K like the owner's manual says to (or whatever your service schedule specifies in the service manual) and don't sweat it. As long as you're within the vehicle's towing specs (for your engine, trans, and rear end ratio) it'll be just fine.

Now, that being said, adding an additional cooler is never a bad thing, watching the temps isn't either. IMHO, as long as you're within the vehicle's tow ratings, neither one is essential.

-Joe

 

[aldive]

Hills? What are hills?

Here in flat Florida, I tow the Jeep in OD.

 

[cabennet]

hills

Manitoba is nice and flat too....

 

[CDW6212R]

The overdrive of almost all automatics made includes a band to hold power. That is called an overdrive band, and that is the weakest link in every such transmission.

Any band is not as strong as a clutch pack, the common trans gear holding component set. The overdrive band cannot hold high stress loads without slipping. The very first overdrive trans made(AOD) was notorious for losing fourth gear, it simply was not strong enough.

For towing, if you can hold speed with less than about 1/4 throttle, then that shouldn't be too much for the overdrive band. What kills the transmission in OD is the slipping of that band.

I have towed with my 302 Mountaineer with OD, but I drove it like I had an egg under the pedal. That was a 170 mile trip to tow my 1999 wrecked Explorer, over good hills of South Carolina.

Keep the throttle below 1/4, or turn off the overdrive. Good luck,

 

[gijoecam]

The slippage occurs at shift time, or if the torque load overpowers the band. On the AOD, it was the shift from 3rd to 4th that put a tremendous amount of stress and wear on that OD band and caused it to fail, like you mentioned. However, once it's shifted into the gear, the band is no longer slipping against the drum, hence the recommendation to leave it in OD if it'll hold the gear. It's the shifting in and out hunting for gears you want to avoid. Generally, with stock tuning on an electronically controlled transmission, the engine can't over-torque that gear and start slipping unless it's already worn out to start with. The programming is such that, should the torque demand exceed the programmed threshold, it downshifts. The AOD was a different beast, and not tied electronically to the ECU to control those loads.

-Joe

 

[CDW6212R]

That's all good to know Joe, I learned my stuff from Gil of TransGo, the man. He explained how all early 80's police cars had big troubles with 4th gear. They evidently early on figured out how to keep them in OD at WOT, and that was death for an AOD back then. The Super Coupe had not come out yet, so there was no "A" overdrive servo, nor the wider OD band of the AODE's.

I agree with the shifting, that's key, but I still don't like the idea of all of the power(high load) through a band. That the trans should shift is nice, but I haven't been impressed by any OEM calibrations. A lot of people have reported some wild character flaws of their transmissions.

I do agree though, don't let the trans make the shifting choices while towing. If it is shifting down and up while at speed and towing, then the shifts are worrisome. I know how to get an automatic to shift without stress, but most people do not. Keep the trans from shifting by not using any significant throttle while in overdrive. If it needs more throttle, turn off the OD. Regards,

 

[rwr1987]

Lots of good advice but what about experience. I have almost exclusively towed a 25 ft Aerolite 7 ft wide 7 ft high (3000lbs loaded) travel trailer with my 98ex xlt 4.0 4x4 extra trans cooler, 3.73 axel (I change the trans fluid and rear axel fluid every year) and many engine mods and now have over 120,000 miles on it with out any issues with the trans and I tow in overdrive all the time. And I get over 15 mpg at 65 to 70 mph!!! My understanding with transmissions is that it is the aero loading and excessive shifting that generate heat. The ex owners manual gives a max trailer frontal area for towing, that is why I bought the 7ft wide 7 ft high trailer to keep my square footage of frontal area well below the max. Good luck!

 

[cabennet]

mileage

thanks for the advice. I towed most of the way in OD, only shifted down when I saw a long hill ahead. No problems. I spoke to my neighbour after we got back. He claimed that mileage would be worse in OD since engine would have to work harder. Any ideas?

 

[joecrna]

Use the OD if you don't shift much. I tow in 4th but thats because of my wieght. It'll shift down from OD on virtually any grade. I only get 7.2 MPG towing at 70. Let the rpms drop and MPG goes up in all but the most specific of circumstances. This may apply to our X's towing at highway speeds but I doubt you would be far enough away from max BSFC (brake specific fuel consumption) to matter. This is why deeper gears don't necessarily hurt too much but the difference between OD and 4th is much larger.

 

[foxy]

People, I haul a 19'6" x8' all the time with a oil temp guage and extra external K&N filter meaning more oil and also a 20,000 btu extra cooler but I rarely if ever travel in OD .Also I change and flush every 25,k and if the travelling was hard even earlier and at this time, touch wood, I've had no trouble Hope this may help Cheers Barry