Matt_Jr
Platinum Member
bake321 said:
Sounds like a heck of a drive. Listen to books on tape, satelite radio, or sing
100 bottles of beer on the wall w/the kids?Should I Be Using Overdrive When Towing?
- Thread starter Rameck
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Sounds like a heck of a drive. Listen to books on tape, satelite radio, or sing
100 bottles of beer on the wall w/the kids?Best to read the owners manual. Unless the vehicle has a lot of torque/horsepower to spare in overdrive (and many SUV/trucks are overpowered these days compared to their predecessors) - you typically don't want to be in overdrive when towing. Overdrive is meant for fuel efficiency at constant speed on flat surfaces. It is not meant for quick accelerations or pulling heavy loads.
Joe
Joe
Builder
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Know your transmission. Find out which gears will lock the torque converter, too!
Matt_Jr
Platinum Member
Builder said:
Many cars and trucks will lock the torque converter at speeds as low as 25mph depending on engine load i.e. coasting, maintaining speed and slight acceleration on level roads. However not all owner's manuals will tell you when the converter will lock and often times the only way to know is to look it up in the service manual or on a scan tool while watching the vehicles data stream. I know I know, lots of people keep saying read the owner's manual and there's nothing wrong with that. The fact is that the owner's manual is written to help you understand how to properly operate your vehicle in most conditions, but it doesn't go into descriptions of how things work and break down what to do to often help you get the most out of it.
For instance, I know a lot of people who would never think to shift a vehicle into a lower gear while going down a steep hill and pulling a load in an automatic transmission. This can save a lot of wear on your brakes and decrease the chances of glazing the pads and rotors and boiling the brake fluid while maintaining control. It might increase a little bit of wear on the trans but I do it in every car and truck I own. I've put almost 150K on one truck, 130K on a car I have, 140 on 2 suburbans and several others and have yet to burn up a transmission. And I do this every single day. I live up on a mountain in northern Va. 2 miles off the paved road on hills that require four wheel drive in dry weather if towing even something as light as a small atv.
The key to making your truck last long is regular preventive maint. I flush my trans with BG synthetic fluid every 25k miles and drive close to 100k miles a year. My Toyota Prius has over 130k miles on it and still has the original brakes on it. My rotors are starting to rust more than my brakes are wearing out. I'll have to replace those when it does finally need brakes but the point I'm making is the more you know how they work the longer you can make them last by having good driving habits that help them work better, more efficiently, and last longer. That includes knowing when to push the tow/haul button, when to turn off the overdrive, and when to pull the shifter down into 3rd, 2nd, 1st, or straight from drive to first. On vehicles with automatic transmissions built after '95, you don't have to worry about overreving the engine 'cause the computer won't let you (unless you're in first and accelerating). Practice leads to confidence which leads to competence, even in something as mundane as pushing a button. I'm going to shut up now.
OP
Rameck
Bronze Member
This is a 2001 Tundra extra cab with a V8 but don't know the cu. in. of the engine. There is no haul mode switch for this that I'm aware of. The hitch is after market. I figured that I'd not be using the OD for up and down hills but some flat land between L.A. and upper Ca. was wondering if usable on the flat areas. The speed is posted max of 55 mph for towing trailers in Ca. and that's fine with me. I feel more comfortable and more in control at lower speeds towing this big of load. Figure, by the time I get to tow it to Washington this summer, gas will be around $4.00 a gal. but don't want to ruin the trans just to safe some money on the flats using overdrive when towing. Appreciate all the input. Still learning.
thanks,
Ralph
thanks,
Ralph
Matt_Jr said:For instance, I know a lot of people who would never think to shift a vehicle into a lower gear while going down a steep hill and pulling a load in an automatic transmission. This can save a lot of wear on your brakes and decrease the chances of glazing the pads and rotors and boiling the brake fluid while maintaining control. It might increase a little bit of wear on the trans but I do it in every car and truck I own. I've put almost 150K on one truck, 130K on a car I have, 140 on 2 suburbans and several others and have yet to burn up a transmission. And I do this every single day. I live up on a mountain in northern Va. 2 miles off the paved road on hills that require four wheel drive in dry weather if towing even something as light as a small atv.
Actually, when in T/H a quick tap on the brake peddle while going down hill tells the trans controller that it should maintain that speed. It down shifts to hold that speed - all by it's self. Works real good - surprisingly so. Then again, that's a GM and not a Toyota so maybe that capability does not cross over?
For the OP - if you don't have a T/H button - I'd agree you are much safer manually sticking it in D and not OD. But on the flats you could probably give it a go with little to no down side. Just don't forget to flip it back to D on uphill grades or to pass.
If you have not be doing regular trans fluid flush's on the truck, I would 100% do it before the tow. Your truck will thank you for it! Power back flush, new filter and if you can $$ go with synthetic fluid. I'd also put synthetic gear oil in the rear differential as towing will heat them up.
jb
Egon
Epic Contributor
Uhh, does your truck have a larger transmission cooler on it like comes with some vehicles that are configured for towing?? If not stay out of overdrive.
When I tow with my truck the OD is always locked out.
When I tow with my truck the OD is always locked out.
Builder
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john_bud said:
My light truck actually has a feature where you pull the shifter stalk back one notch to the "M" (manual) position and then you can push the "+/-" toggle switch on the shift stalk and shift it like a manual transmission with no clutch. Of course, in tow haul it downshifts automatically.
HarryVanderpool
Gold Member
So far, everyone has left out a very importand part of the equation:
What is your final drive ratio?
My 7.3 PSD has a 4:88 final drive.
I tow 8800# all over Oregon in overdrive.
If i didn't, I would have to push 2500 rpm just to reach 50 mph.
When I'm on slow windy roads I lock out OD.
Otherwise, its just another gear.
I cruise at 2000 RPM which is 54 mph. (in OD)
What is your final drive ratio?
My 7.3 PSD has a 4:88 final drive.
I tow 8800# all over Oregon in overdrive.
If i didn't, I would have to push 2500 rpm just to reach 50 mph.
When I'm on slow windy roads I lock out OD.
Otherwise, its just another gear.
I cruise at 2000 RPM which is 54 mph. (in OD)
Builder said:
Yeah, that is a super nice feature on the newer 6 spd allisons. My archaic 5 speed alli could use that and the 2nd OD!
Harry, 2000 rpm at 54 mph??? Ouch! And you only tow 8800# with it? Double ouch! I used to tow that much with my yr 2000 1/2 ton auto 3.73 gears and got 10-11 mpg. BUT.... Taxconsin is mostly a good bit flatter than Oregon. While expensive to run, I'll bet it's a stable rig.
jb
HarryVanderpool said:So far, everyone has left out a very importand part of the equation:
What is your final drive ratio?
My 7.3 PSD has a 4:88 final drive.
I tow 8800# all over Oregon in overdrive.
If i didn't, I would have to push 2500 rpm just to reach 50 mph.
When I'm on slow windy roads I lock out OD.
Otherwise, its just another gear.
I cruise at 2000 RPM which is 54 mph. (in OD)
Isn't it amazing that the trucks today have so much spare HP/torque that you can do that (compared to what we had 20+ years ago). Just think - the 7.3 PSD was an early entrant to the torque wars (with a torque rating of 400 something). The newer trucks have rated torques above 600.
JD4610
Member
In my years as a Ford technician (with a degree in Automotive Technology to boot) I have never seen so much misinformation, misconceptions, and downright BS surrounding any automotive subject as I have with the mysterious and majical "overdrive." Transmissions with overdrive have been around in numbers since the late 1970's but a majority of the public still refuses to believe that overdrive is nothing more than another gear ratio available from the transmission. It has nothing to do with special trans fluid, torque converters, or the transmission fairies.
In the old days we had auto transmissions that had three speeds, which were derived from a single planetary gearset. A simple planetary gearset will give you three speeds: A low or first gear, an intermediate or second gear, and direct drive. In first gear the output shaft spins slower than the input shaft, which is driven by the torque converter, due to the gear ratio provided by the planetary set. Thus, first gear is UNDERDRIVEN: Output is slower than input. Second gear is the same, except the ratio is slightly changed to provide more output speed, but it is still UNDERDRIVEN. Now, third gear is different in that the planetary members are locked together and perform no torque multiplication. The output speed of the transmission is exactly the same as the input speed, that is, it is in DIRECT DRIVE. In DIRECT, if the engine is spinning at 3,000 rpm, so is the output shaft of the transmission.
When the need for improved fuel economy became an issue, engineers had to find a way to slow the engine down without reducing normal cruising speeds. This could be accomplished by changing the axle ratio of the vehicle, but this change would also result in much slower acceleration and decreased towing capacity. The final solution was to add an "extra" gear to the transmission, one that would allow the output speed of the transmission to be higher than the input speed. Therefore, the transmission would be OVERDRIVEN. This is where the term "overdrive" comes from: it is simply the mode that the transmission is operating in. Overdrive is accomplished by either adding a second planetary gearset to the trans or by using a "Ravigneaux" gearset (try Google.) This trend continues today as five and six speed automatic transmissions are common, many of which have TWO overdrive speeds.
So, why is there a switch for turning overdrive off? The same gear mechanism that slows the engine down also drastically reduces the amount of torque that can be delivered to the wheels. Under a heavy load at freeway speeds, the engine may not produce enough power to maintain road speed for that gear and will downshift to the next lower gear. The rpms will rise and power increases. As you accelerate up to speed, the transmission or powertrain computer will sense the reduction in throttle as you try to maintain your target speed. Since you are letting off the throttle, the transmission will shift back into top gear (overdrive.) With the engine slowed down again, it won't produce the needed power to maintain speed, so you push farther down on the throttle and the transmission will again downshift to get the engine back up to speed. This upshift/downshift cycle continues and each shift builds up heat due to friction in the trans. Heat is bad for a transmission so to prevent these damaging shifts engineers give us a way to lockout overdrive either by a switch or a separate gearshift position. Of course, this makes the engine rev much higher and your fuel mileage will plummet.
You'll notice nowhere above is there any mention of the torque converter. Why? Overdrive has nothing to do with a lock-up torque converter. As a matter of fact, Ford's first major overdrive transmission put into production, the AOD (Automatic OverDrive,) didn't even HAVE a lock-up torque converter. Ford's prolific Super Duty trucks with the 7.3L have a four-speed auto with fourth-gear overdrive but will lock their torque converter in second, third, and fourth gear.
The simple fact is that unless your transmission is "hunting" for gears (repeatedly shifting up and down while trying to maintain a set speed) there is no reason to turn off or lock out overdrive, regardless if you are towing or not. I have yet to see an owner's manual that fails to explain this in this manner.
So please, before perpetuating the "Freemason's guide to the secret Overdrive" do a little research and find out how overdrive works from a shop manual and help me put an end to overdrive slander.
Jay
In the old days we had auto transmissions that had three speeds, which were derived from a single planetary gearset. A simple planetary gearset will give you three speeds: A low or first gear, an intermediate or second gear, and direct drive. In first gear the output shaft spins slower than the input shaft, which is driven by the torque converter, due to the gear ratio provided by the planetary set. Thus, first gear is UNDERDRIVEN: Output is slower than input. Second gear is the same, except the ratio is slightly changed to provide more output speed, but it is still UNDERDRIVEN. Now, third gear is different in that the planetary members are locked together and perform no torque multiplication. The output speed of the transmission is exactly the same as the input speed, that is, it is in DIRECT DRIVE. In DIRECT, if the engine is spinning at 3,000 rpm, so is the output shaft of the transmission.
When the need for improved fuel economy became an issue, engineers had to find a way to slow the engine down without reducing normal cruising speeds. This could be accomplished by changing the axle ratio of the vehicle, but this change would also result in much slower acceleration and decreased towing capacity. The final solution was to add an "extra" gear to the transmission, one that would allow the output speed of the transmission to be higher than the input speed. Therefore, the transmission would be OVERDRIVEN. This is where the term "overdrive" comes from: it is simply the mode that the transmission is operating in. Overdrive is accomplished by either adding a second planetary gearset to the trans or by using a "Ravigneaux" gearset (try Google.) This trend continues today as five and six speed automatic transmissions are common, many of which have TWO overdrive speeds.
So, why is there a switch for turning overdrive off? The same gear mechanism that slows the engine down also drastically reduces the amount of torque that can be delivered to the wheels. Under a heavy load at freeway speeds, the engine may not produce enough power to maintain road speed for that gear and will downshift to the next lower gear. The rpms will rise and power increases. As you accelerate up to speed, the transmission or powertrain computer will sense the reduction in throttle as you try to maintain your target speed. Since you are letting off the throttle, the transmission will shift back into top gear (overdrive.) With the engine slowed down again, it won't produce the needed power to maintain speed, so you push farther down on the throttle and the transmission will again downshift to get the engine back up to speed. This upshift/downshift cycle continues and each shift builds up heat due to friction in the trans. Heat is bad for a transmission so to prevent these damaging shifts engineers give us a way to lockout overdrive either by a switch or a separate gearshift position. Of course, this makes the engine rev much higher and your fuel mileage will plummet.
You'll notice nowhere above is there any mention of the torque converter. Why? Overdrive has nothing to do with a lock-up torque converter. As a matter of fact, Ford's first major overdrive transmission put into production, the AOD (Automatic OverDrive,) didn't even HAVE a lock-up torque converter. Ford's prolific Super Duty trucks with the 7.3L have a four-speed auto with fourth-gear overdrive but will lock their torque converter in second, third, and fourth gear.
The simple fact is that unless your transmission is "hunting" for gears (repeatedly shifting up and down while trying to maintain a set speed) there is no reason to turn off or lock out overdrive, regardless if you are towing or not. I have yet to see an owner's manual that fails to explain this in this manner.
So please, before perpetuating the "Freemason's guide to the secret Overdrive" do a little research and find out how overdrive works from a shop manual and help me put an end to overdrive slander.
Jay
Egon
Epic Contributor
Lets not forget the temperature gauges that give a good indication of what is happening with the turbo, transmission and the engine. Many who tow regularly have added these if they did not come with the vehicle.
I don't have them but I would like them.
I don't have them but I would like them.
Matt_Jr
Platinum Member
JD4610 said:
JD4610, I'm not disagreeing with you here, like I said before I'm no expert. Although transmissions are not my speacialty I do recall on several occasions while testing many ford trucks one of the diagnostic procedures was to drive the vehicle around 40mph(not exactly sure on speed) and cycle the overdrive switch, cylce again, and very lightly tap the brakes(enough to cycle the brake switch). Then watch the rpms to see that they go up around 200 rpm both times. This was to test the lockup converter on the 4R70W AOD if I recall correctly. The reason you do this at 40mph(or lower, don't recall exactly), is because if you were going faster it would downshift the trans into a lower gear(cycling the switch). Like I said, not disagreeing with you on the higher gear reaching a ratio of close to 1:1, but the only gear you don't want the converter to lock in is 1st(would cause engine to stall when stopped) but having the converter unlocked all the time would cause excessive heat buildup in the converter. Now, a little more detailed than my last description-the torque converter will still lock up even when OD is cycled off, but dissengages on lighter throttle application. This could be mistaken for a downshift but really isn't at low speeds. Now at highway speeds it will leave the vehicle in third gear as opposed to 4th and this is where the fuel mileage really suffers. Not just from the converter unlocked.
I totally agree with you about the gear hunting back and forth, and the converter fairy but as a proffesional I would appreciate it if you correct me if I'm wrong on the other stuff. Ain't too proud to admit when I'm wrong, and would rather be corrected than assume I'm right. Besides, we all know what "ASSUME" is when it's broken down
.Renze
Super Member
With a 2 ton load, i try to keep my TDI at 2000 rpm in 5th gear (overdrive) because that's where it has enough torque to get over a hill or so. at 80 km/h (legal towing speed in Holland) it does only 1500 rpm which is too low in the torque band to tow. I like to tow at 110 km/h anyways.
This 2.5 TDI has enough torque, and is sturdy enough to be working at 80% of power for extended periods of time. If i chipped it to 220 hp i'd rather not use all that power when towing, but at factory standard 140 hp its relatively safe to just use what its got.
If i had a gasser, i'd probably tow in 4th gear because of the different torque band... or do the gasser 850's have different gear ratios anyways ??
This 2.5 TDI has enough torque, and is sturdy enough to be working at 80% of power for extended periods of time. If i chipped it to 220 hp i'd rather not use all that power when towing, but at factory standard 140 hp its relatively safe to just use what its got.
If i had a gasser, i'd probably tow in 4th gear because of the different torque band... or do the gasser 850's have different gear ratios anyways ??
HarryVanderpool
Gold Member
>>>"Freemason's guide to the secret Overdrive"<<<
JD4610, now that was really funny!!
Like I said; Overdrive is just another gear.
JD4610, now that was really funny!!
Like I said; Overdrive is just another gear.
JD4610
Member
Hey Matt, that wasn't specifically directed at you, sorry if it sounded that way. It was pretty late when I typed that.
My specialty was/is EEC systems, gas, diesel, and hybrid. There are so many possibilities with the software/hardware that we have today that it is always hard to keep things in focus. With a simple change to the software, engineers can completely change the character of an engine and trans, as we've seen through the history of the 7.3L and 6.0L. These changes aren't always for the better, and I've dealt with many customer complaints after upgrading to "improved" software from the factory.
I guess my advice, for what it's worth, is to take care of the trans by avoiding "hunting" for gears, keep the trans fluid fresh ( I change mine every 20k miles,) and to keep the trans cool by not hammering on it at low speeds, especially while towing or off road. I would also highly recommend a trans temp gauge for anyone that tows with their truck.
Jay
My specialty was/is EEC systems, gas, diesel, and hybrid. There are so many possibilities with the software/hardware that we have today that it is always hard to keep things in focus. With a simple change to the software, engineers can completely change the character of an engine and trans, as we've seen through the history of the 7.3L and 6.0L. These changes aren't always for the better, and I've dealt with many customer complaints after upgrading to "improved" software from the factory.
I guess my advice, for what it's worth, is to take care of the trans by avoiding "hunting" for gears, keep the trans fluid fresh ( I change mine every 20k miles,) and to keep the trans cool by not hammering on it at low speeds, especially while towing or off road. I would also highly recommend a trans temp gauge for anyone that tows with their truck.
Jay
HarryVanderpool
Gold Member
VA_Joe said:
Compared to some other newer rigs, the stock 7.3 is a dog.
But, thats what I have and thats what I'm going to have for a long time.
Theres 175000 miles on the clock right now. (stock original tranny)
When it finally conks out, I will install one of them custom beefy trannys so that maybe I CAN bump the horses up a teensy-weensy bit.
The low gear ratios and 4WD really make crawling around in fields a breeze.
Here's a pic of my rig with 88 bee hives on back:
http://img.photobucket.com/albums/v202/Shallotman/DSC00473.jpg
em14
Platinum Member
HarryVanderpool ... I sure would hate to bump into that load ....
Leo
Leo
HarryVanderpool said:
And compared to what came before the 7.3 PSD it is a superstar. It's a proven engine that will last a very long time (with more than enough performance to meet most demands). With the newer engines and their stratospheric torque ratings - only time will tell (both Ford and Chevy had their share of growing pains when first released).
Joe
