Okay all you truck experts, here's my question...  Is it okay to use the overdrive gear while pulling a trailer on flat interstate?  What about the cruise control?

I ask this because I have a neighbor who complains that she gets less than 10 mpg while pulling her trailer.  She says the guys that sold her the truck told her to keep the OD off while pulling her trailer.  But that means she is running well over 3,000 RPMs while going down the highway...thus the poor mileage.

She has an '01 F-150 (gas motor) and an aluminum 2H GN with a small LQ (no bath).

I have a '97 F-250 (PS diesel) and a steel 3H GN with a small weekender.  Once on the flat highway, I turn the OD on and set the cruise.  I get around 15 MPG, which is only a little less than without the trailer.

Here's some previous threads about the subject.

http://www.horsetrailerworld.com/forum/thread-view.asp?threadid=11907&posts=14

The answer is yes and no. Yes it can be done with some trucks and some terrain, and no it can't be done with other rigs. With a lower HP truck and light weight transmission, the truck may start to cycle between high gear and OD when on a hill. If it is allowed to continue, this oscillation can be rough on the transmission, and the driver's nerves.

If the light weight truck is into a head wind, up even a slight but long grade, and is pulling hard, I would switch out of OD. Allowing the engine to rev more and pull less hard will use more gas, but be easier on the equipment. The radiator water temps are shared by the engine and transmission. The harder the engine works, the more heat is transferred to the radiator. This is the starting temperature for the transmission fluid. The harder the transmission works, even more heat is added to the fluid. Without a synthetic fluid, and an auxiliary cooler, the transmission can be damaged by the excessive heat.

The larger trucks with a towing package have all the necessary coolers and rugged transmissions. As long as they have the power to pull the grades, an OD setting will do no damage. When there isn't sufficient torque, and you're running in cruise, the computer will effect a downshift.

I have a chip in my diesel, allowing me to pull most of our grades in OD with no downshifting. With a synthetic transmission fluid, my transmission temperatures never overheat or even get near a dangerous level.

I use the OD and cruise at every opportunity with the truck. When I pulled with a gas Expedition, I was more selective about the OD usage. I used it when the conditions were apropos, and deselected it when the engine was working too hard.

You have to be attune to how the tow vehicle is handling the load, and drive accordingly.

Gard

Her truck really needs to have the od OFF while towing!  Not near enough engine to stay in the power band and will cause more wear and tear shifting in and out of overdrive.

Your truck is just fine on the hwy with the overdrive ON! Just to add to what gard added.  If you was to install something like a TS performance 6 pos, 4 bank chip into your truck, you will notice a fuel mileage and power incease and would be able to leave your truck in OD most of the time.....

Thanks guys.  I knew I could count on y'all for some insight. 

Regarding the chip...do you think it would be beneficial in my 12 year old truck with over 200K miles??  And what does something like that cost??

YES!  I am in the used car buisness and deal mainly in older diesel trucks.  The main thing to remember that it is all in YOUR driving habbits!

What I start with is the exhaust and air flow work so the truck will breath better.  The factory downpipe on the 94.5 to 97 Powerstroke diesels are smashed flat behind the turbo and really hurts performance.  I used this part from ebay Item number: 270400421219, most muffler shops can install these and will work with the factory system if you do not like the deeper sound of 4" pipe.  Then on the intake side I started using S&B intake kits with good results in power and fuel mileage. 

I have had really good luck with the TS Performace chip and have been buying them from ebay Item number: 230355735346.  I order mine with stock, 50hp, 75hp, 100hp, high idle and valet.  I have been buying them form this seller anywhere from $200. to $225. depending on his mood.  I run mine on 75hp while towing but I have the intake upgrades and complete exhaust work done (3" downpie and 4" straight pipe all the way back.  If you only do the down pipe and leave the stock pipe I would only use the 50hp while towing!

The truck I was using to tow with was a 1997 Ford F-350 crew cab dually automatic with a 187-k miles, 4.10 gears.  Truck was getting 12 loaded stock, 15 empty.  After above goodies was added set on 75hp mileage loaded went up to almost 15 and 18 empty!  The man I sold the truck to lives down the road from and still has mods done with 212-k miles!

So to your question with full modifcations (as I would do) you are looking around $750. this includes chip, intake kit, complete exhaust upgrades and labor.

 " Then on the intake side I started using S&B intake kits with good results in power and fuel mileage." 

HTB, you certainly are knowledgeable about the chip and diesel modifications. With your hands' on experience, why have you chosen the S&B intake kits?

I've installed a K&N kit and was disappointed. It was noisy, very loud under a load and actually made no difference in mileage. On one of the diesel forums, it was actually rated poorly, in its ability to block dust from entering the intake system.

I soon removed the K&N system, reinstalled the original box and installed a NAPA filter that was recommended within the diesel forums. It is again much quieter, and hopefully doing a good job in filtration. Again, there is little or no noticeable change in mileage between the two systems, but a large amount of audible comfort. I have a 3 1/2" down pipe and 4" stainless system with only a small, straight through "muffler".

I've never installed or actually seen the S&B system, but in the advertising materials I've reviewed, it looks quite similar to the K&N. Other than the actual filter, are there any reasons why one would be any more efficient than the other? Does it have the open air box design like the K&N which contributes to the large amount of intake noise? I wish these were designed as a closed box, with an under hood, fender sourced cool air supply like some systems.

Thanks for your excellent technical postings. We need someone within this forum with hands on experience to offer this type of advice. There are a few naysayers, who, with advice from their best friend's, uncle's mistress, whose last boy friend once read, that modified chip installations will blow up your motors.

Our forum is not dedicated to the performance type of modifications that will assist in quarter mile times. We want reliability, more torque, better mileage and drive ability. With the correct advice and equipment installation, we can have it all.

Thanks again Kelley. Keep up the good work.

Gard

HTB, you certainly are knowledgeable about the chip and diesel modifications. With your hands' on experience, why have you chosen the S&B intake kits?

I've installed a K&N kit and was disappointed. It was noisy, very loud under a load and actually made no difference in mileage. On one of the diesel forums, it was actually rated poorly, in its ability to block dust from entering the intake system.

I soon removed the K&N system!

Yes, I was using the K&N Intakes, but after the S&B system came out and reveiwing their test I thought I would try it out. It is pretty much a complete inclosed housing (does not suck in hot air from under the hood, like the K&N does) with larger free flowing duct work going to the turbo and larger inlets going into the fender. Is is louder than stock and can here the turbo, but not agravating like the K&N systems are. Check out their website or I think you can go to www.truthaboutfilters.com for test results.
They actual do not claim to have mileage increase, but with my own personal use on the 7.3 Powerstrokes and my 07.5 Dodge with the 6.7L Cummins I see an increase. The Dodge was getting 10.5 to 11 loaded and almost 14 unloaded, after just the S&B intake kit, I was getting 11.3 to just over 12 loaded and right at 15 unloaded. Then after I did some other stuff and parts fell off of the exhaust system and a program was install and set on 120hp the truck now gets almost 14 loaded and almost 19 unloaded.

My opinion anytime you can add a few hp by pulling in cooler air vs. hot air from under the hood is free hp which means you will not have to be working the engine as hard which in turns will save you fuel mileage. Each truck and each drivers habbit will have diffenent results. The 97 F-350 that I mentioned in an earlier post that I sold, that man is actually getting better mileage than I was getting. But he drives with the cruise set on 65mph everytime he can on the hwy....

HTB, Kelley

Mileage should be worse in OD not better as you are in a lower gear and rpm's should be higher. In my Duramax I get 1 less mpg in OD.

I use OD with a heavier trailer and standard with a lighter trailer

The OD ratios LOWER your RPMs, not raise them. If your engine is working too hard in OD, it may in fact, use more fuel than while in a lower gear with a higher RPM. This is more true of a gas engine that  has to produce a higher RPM to develope its HP than a diesel, that starts and maintains its torque range at a much lower RPM.

"I use OD with a heavier trailer and standard with a lighter trailer" 

This is just the opposite of most drivers

Gard

The usual answers include exhaust, intake and chip changes. I personally don't know of anyone who has done these mods or how much improvement was made. The 10s are not noted for mileage, they rev high and work hard to make the power.

When Hogtownboss checks in, perhaps he can offer more insight. Have you checked any of the truck/RV  forums? It's a widely used motor and must have some info available.

I just found this site and a question similar to yours:

http://tunertools.com/forums/showthread.php?t=69

BOL Gard

Correction, I was thinking tow haul mode which I use when pulling a heavy trailer. My bad. Old age is getting to me.

Is that temp reading being taken pre-turbo, after turbo before after cooler, or after, after cooler...? Turbocharger build alot of heat in the intake, higher intake pressures make for higher temps.... Thus the reasoning behind the after cooler. I would say that 130 number sound good for an intake temp... We used to see as much as 400 degrees on the pulling tractor, but that was only for 5-10 seconds.

All of the infomation I have seen airraid is one of the worst intake kit out right now.  I have never used or owned one.  I have used K&N's (who makes filters for Banks) but they are a open unit!  Anyitme you can draw air from outside of the hood you will do more good for your engine, performance and even fuel mileage!  Proven fact, better performance, better fuel mileage!

I think the S&B will help you, along with the Banks Kit, but the Banks is almost doulbe the price!

The 6.0'S ARE FINE, people just do not understand them and listend to the Ford dealers and what they read on line.

HTB