I have a 98 F150 4x4 extended cab with 5.4 auto 3:55 rearend and factory towing package. I tow a 20.5 foot holiday trailer that weighs about 4000lbs. Can I tow in overdrive or will this damage my transmission? Thanks for your advice.
Mitch

 

do not tow in overdrive ever

 

I disagree. The O/D disable is there to prevent the tranny to overheat by constantly shifting between O/D and 3rd gear. If the truck can pull it in O/D, let it! It'll save you gas, and the tranny should actually run cooler in overdrive.

 

Look if the tranny keeps shifting while towing you'll do damage. If there is alot of hills tow with the OD off. I tow a 18 ft fiberglass boat with my 99 F150 SC 5.4 4X4. unless Iam on the thruway where the speed is 65 to 70mph, and there I usually tow in OD, but you have to be carfull on the throttle so you do not do alot of shifting. On the back roads where the speed is 55 mph I tow with OD off.

 

My truck is a 98 F150 4x4 SC 3.55. I have been towing a 2800 lb Miata on a 1500 lb trailer back and forth between florida and Michigan for five years. Generally I tow in OD with very little down shifting even through KY. Tn.and north Ga. Exceptions are the steepest mtns. and strong head winds, under those conditions I disable OD. Your load may have a much higher profile and therefore more drag than mine, my rule of thumb is if the truck downshifts too often I disable the OD. When I tow my boat rig which is over 6000 lb and has considerable wind resistance I only use OD on flat roads and little or no headwinds. My mileage towing the car, at about 65/75 is 12.5.

 

Opps, I neglected to say what engine I have, it is the 5.4L. Also, the bed is usally fully loaded. One of these trips I will have to put the rig on one of those truck scales and get an accurate total weight.

 

The rule of thumb is if the tranny is shifting up and down then hold it in the low gear until it can hold the upper gear. Shifting creates heat which is the enemy of transmissions.

 

I tow a 4600 LB trailer with my '02 5.4l 3.55 diff and 17" wheels.
I find that every time I try to tow in O/D, even though I can and RPM's drop considerably, that I still need to put about the same amount of gas pedal into it unless of course I'm going down a good incline or have a real good wind at my tail. You have to work the engine a little harder in O/D, therefore it takes the same amount of fuel as when you're out of O/D.
Out of O/D, it's not working as hard, so the same amount of fuel will run the motor at a higher RPM. I think I'd rather run steady at 2400 RPM and 60 MPH than run at 2100 RPM and have to keep giving it a little more pedal at every little incline.

 

Well, you're right about being a little easier on the engine, but I disagree about using the same amount of gas. First of all, when your engine is running at 2400 RPM, the fuel injectors are injecting gas into each cylendar 2400 times, this versus 2100 times. Now, because you have to use a little more throttle, the injectors are pumping a little more gas at 2100 than if it were not under load at 2100.

But, the purpose of overdrive is to lock out the torque converter. The torque converter consists of two spinning rotors with the only thing connecting them being transmission fluid. The crankshaft spins one, and the faster it turns, the higher percentage of power is transferred to the tranny, but it is never 100%. When the tranny goes into overdrive, it locks the two rotors with a clutch, so 100% of the power is transferred to the tranny, therefore much more efficient.

So, it would be best for fuel efficiency to leave it in O/D if the truck can do it without shifting a lot.

 

2400 rpms would be 1200 squirts, not 2400. The engine fires on every other up stroke, not on each. that's why it's called a 4 cycle. Just a mathematical technicality

 

You're right, OK, got me on that one. The concept still stands, however.

 

I've been told ... towing in overdrive even if she stays in OD w/out shiftin around, it creates more heat and stress than jus turnin more rpms ? true..or..false?

 

The biggest thing inside an automatic tranny that causes heat is the tranny shifting around a lot. When the tranny shifts, it actually has friction clutches that engage and disengage, and every time that happens, it generates heat.

Furthermore, back to one of my previous posts about power being lost in the torque converter. Where does the energy go? The bit of power that is lost is being transferred to the tranny fluid in the torque converter in the way of heat energy.

From a less technical point, we know that the tranny is most efficient in O/D. When it isn't in O/D, the energy lost has to go somewhere. We know that it doesn't remain in kinetic(movement) form, so it has to go to heat, which is disspated by the radiator. This is why manual trannys are more fuel efficient, becuase very little energy goes to heat. There are no tranny cooler lines running to the radiator on a standard tranny because it doesn't need them! This is why standard trannys use gear oil instead of tranny fluid!

Hope this helps!

 

drive and overdrive both can get the tq converter into lockup or no slippage no loss no additional heat created at that point . The reason not to tow in od is that the planetary gears are held in position by shifting bands which must be held in place by fluid pressure od acts like a big lever that being the rear tires have more leverage on the transmision and push back with greater force the motor uses more torque to turn the wheels and this extra force creates more heat . the shifting is a sign that the engine is working to hard and the transmision shifts. the shifting is not what causes the heat but the extra force the load has on the engine in od . this also causes the engine to run hotter and if the truck has no aux tranny cooling then the trans will run hotter as the cooling is only done by the radiater. So the answer IMO is if the trany needs to shift constintly keep od off so things dont get a chance to heat up if the road is flat and the load isnt a huge drag and you do proper matinance on the truck you should be good as some have posted. Keeping od off always while towing is considered by most to be good insurance against trans failure. Try finding people that have had failures and dont make their mistakes. First mod to any car or truck i get is the trany cooler . several cars i have had without the cooler had tranys die. that doesnt happen to me any more.

 

I tow a 30ft. travel trailer (5300 lbs. empty) with my 01 S-Crew 4x4 5.4l. I have towed in and out of O/D. with it out of O/D I'm taching 3000 at 70-75 in O/D i'm taching 2500+ at 70-75 but I get blow by on the tranny. I guess this comes from heat ? I have the factory trans cooler and oil cooler but the truck has 90,000 miles on it. my gas mileage doesn't change much either way (8-10 mpg)
Mike
01 S-Crew 5.4l 4x4