Overdrive: When is it necessary

[Pony]

Boat: 14ft Alumacraft; 25hp johnnie outboard<br /><br />Truck: Dodge Dakota; Magnum series V6; towing package<br /><br />I think the boat and motor weigh somewhere around 800 to 900 lbs....maybe someone can verify that. I ask this question because i just had a debate with my grandpa about it. I always turn the overdrive off when pulling ANYTHNG...but he insisted that the boat is light enough that as long as one is careful when accelerating and doesnt use cruise control it should be fine. What do you guys think?

 

[rg33]

Re: Overdrive: When is it necessary

try a test drive with the OD and see if it is hunting for the correct gear. AT that weight it may be fine with minimal to no hunting. Living where your are, try going up 41 a ways and see how it handles the varying road.

 

[milkyway]

Re: Overdrive: When is it necessary

I have v-8 rated to tow 7,400# and I tow 6300#. I used to tow with the overdrive ON and it did not really give me a problem but then I noticed that I need to step on the gas longer and deeper to accelerate the car. Then I tried driving with Off. Now car runs and pulls better, giving better mileage. In your case, 900# is just like having 5 passengers riding with you. i think you can use the overdrive. But make your own observation like what I did. If your truck pulls as hard and changes gears as fast and revs the rpm equally, then overdrive may be fine.

 

[Pony]

Re: Overdrive: When is it necessary

With the overdrive OFF the rpms are up about 800 or so from with it on. In this truck when overdrive kicks in it throws you back pretty good. I've pulled with it on and off, just am not sure what im doin to the tranny either way.

 

[mrloring]

Re: Overdrive: When is it necessary

Confusion but isn't <br /><br />Overdrive = Shifting a manual into 5th gear<br /><br />Shifting that throws you back would be commonly called "passing gear" = shifting a manual into 3rd gear.<br /><br />Until recently all of my vehicles have been manual tranny

 

[Pony]

Re: Overdrive: When is it necessary

overdrive in an automatic is shifting into the highest gear just like a manual tranny (only its electronic and the function itself can be turned off when you dont want to be shifting back and forth while pulling a load)<br /><br />"How to use overdrive<br />Generally speaking, overdrive (O/D) is the highest gear in the transmission. On most cars the automatic transmission has 3 speeds and Overdrive (forth speed). Overdrive allows the engine to have less rpm with higher speed in order to have better fuel efficiency. When you switch it on, you allow the transmission to shift into overdrive mode after the certain speed is reached (usually 30 - 40 mph depending on the load). When it's off, you limit transmission shifting by third speed.<br />In normal driving condition the overdrive should be always on.<br />You may need to switch it off if you drive in mountains area.<br />[The automatic transmission automatically shifts from OD to the 3-th gear when it feel more load. When it feels less load it shifts back to the O/D, but under certain conditions, e.g: driving uphill or towing a trailer, the transmission can not decide to stay in OD or to shift into 3-th speed and it starts to shift back and forth. That's the time you may switch it off and help the transmission to decide.] .<br />You also may need to switch it off when you want to slowdown using the engine braking, for example, driving downhill"<br /> -from samarins.com

 

[Bondo]

Re: Overdrive: When is it necessary

I'd say your Grandpa is a Very Smart Man,........<br /><br />Listen to Him............

 

[Silvertip]

Re: Overdrive: When is it necessary

This discussion (like so many others on this topic) will likely go on and on and that's what forums are for. Besides overdrive, automatic transmissions have lock-up torque converts that are also controlled by the ECM. Torque converter lockup is not a gear but is simply a clutch that physically locks the engine to the input shaft on the tranny. What many people feel when towing (or otherwise) is the converter locking and unlocking. A 400 or so RPM rise or fall at freeway speed is the converter locking and unlocking. Overdrive causes a 20% or more change in RPM. If both events happen you can see a 1000 RPM or greater change in RPM. I've owned a Dakota V6 in the past and was towing a little heavier boat with it at the time and I can assure you, that engine is not a powerhouse. On flat ground, it should tow OK in OD but if you are not keen on whats going on with the tranny, turn OD off. Chrysler trannys are not noted for taking much abuse.

 

[tr918]

Re: Overdrive: When is it necessary

I have a Toyota T100 with the small 3.0L v6. I use the OD on the straits and turn the electronic OD off on the hills. Boat, trailer and fuel weigh roughly 1200-1800lbs. It keeps the torque converter happy.

 

[mrloring]

Re: Overdrive: When is it necessary

Originally posted by pony85:<br /> With the overdrive OFF the rpms are up about 800 or so from with it on. In this truck when overdrive kicks in it throws you back pretty good. I've pulled with it on and off, just am not sure what im doin to the tranny either way.

Thanks for the clarification pony, that is what I thought. The confusion came from the quote

In this truck when overdrive kicks in it throws you back pretty good.

wouldn't it throw you back when it kicks OUT of overdrive. <br /><br />Checked and my car has it but doesn't call it overdrive. Gear shift says Drive, 3, 2, 1, but difference in rpm's from drive and three. <br /><br />PS a freind of mine (female) hits that button like it is NOS or something. Example going up a hill and need extra power hit the overdrive button. I tried to tell her that was not how it works, but she doesn't listen. She swears it helps.

 

[imported_Curmudgeon]

Re: Overdrive: When is it necessary

What does your owner's manual suggest? Mine says don't use OD when towing ...

 

[Pony]

Re: Overdrive: When is it necessary

The owners manual isnt perfectly clear. basically leaves it up to the driver....<br /><br />"To reduce potential for automatic transmission overheating turn the overdrive OFF when driving in hilly areas.........to eliminate excessive engine shifting"<br /><br />Upinsmoke- I sort of disagree with your generalization of the V6 dak.....I have pulled boats much heavier than the one i have (16ft tri-hull fiberglass). My dad used to pull that boat with a silverado we used to have with the basline V8 and he said my truck pulled it much much better. It maybe since i have the towing package....but for a V6 this truck pulls plenty well. I dont plan to use OD on hills or anything, then i will definately turn it OFF. maybe you had the older V6??....the 3.9 i have has 75hp more than the previous 3.9L engines.

 

[JB]

Re: Overdrive: When is it necessary

Overdrive is never "necessary".<br /><br />Every vehicle is unique, as is every trailed load.<br /><br />Some makers tell you to never use OD when towing, others say don't use it in the mountains. Some leave the decision up to the ECM, and if you don't like it hunting you turn the OD off.<br /><br />There is no "rule of thumb" that fits every vehicle and situation. The best control you have is an experienced driver who understands what he is doing.

 

[Pony]

Re: Overdrive: When is it necessary

Thanks Jb- those were pretty much my thoughts before i posted this thread originally....I just wanted to know what others do, just because obviously there is something worth debating given that me and my grandpa were discussing it. <br /><br />I agree that OD is never really a necessity, but its nice to have. Like you said each situation is different. <br /><br />I think what I will end up doing is drive with OD on, to keep the rpms down which should help with mileage right??? I will just control the driving in such a way that I keep the transmission from shifting into OD when I am accelerating etc. Not too hard to do....Plus I just wont use cruise control, since OD kicks in a lot when using that.<br /><br />Bondo- you're right my grandpa is a very smart man. I generaly go to him first with any questions I have about lots of stuff. Someday I hope to be half as knowlegeable as that man

 

[Silvertip]

Re: Overdrive: When is it necessary

Pony - Yes I did have the older Dakota with the 3.9 V6. Indeed horsepower has increased on that engine but torque has not. If your truck works for you thats fine but mine was a slug to put it bluntly. That said, my discussion was about use of overdrive. What makes a tow vehicle great rather than just getting by is selecting the proper axle ratio. Most trucks are sold today in standard form with fuel mileage in mind. Unfortunately the axle ratio they install is not conducive to good towing. Also, just because one orders a towing package does not mean you have a towing axle ratio. It is rarely included in the package. Towing packages typically include the hitch, wire harness, heavy duty radiator, alternator, and sometimes an external tranny cooler. Sorry you misinterpreted what I said but it doesn't matter what tow vehicle you have or how its equipped, if the transmission is in and out of lockup and in and out of overdrive on a frequent basis while towing, you better lock out the overdrive. The smaller the engine the more important this becomes.

 

[Pony]

Re: Overdrive: When is it necessary

I understood what you said Upinsmoke....and I agree 100% about the OD, and i was simply wondering based strickly on performance which V6 you had.<br /><br />The sheets I have in front of me show 190 ft/lbs of torque on the 3.9L before mine.....mine however (according to this chart: consumer reports) shows 225 ft/lbs of torque. And I understand that axel ratios make a difference....I do in fact have a 3.90 gear ratio with 4 wheel drive. sorry u thought i was misunderstanding you...didnt mean for it to look that way.

 

[phantoms]

Re: Overdrive: When is it necessary

Overdrive simply means the transmission is over-driven. Drive (3rd normally) is usually 1:1 ratio. Overdrive means the output shaft of the trans turns faster than the input shaft (engine side). The output loses a lot of torque in doing this. Theoretically, Drive's input power is even with output power (actually, there are loses), 1st and 2nd are underdriven and the output power is multiplied. Most vehicles state to tow with overdrive off because overdrive is designed to save fuel and accommodate a vehicle under normal loads. Towing is not under normal loads.

 

[jtexas]

Re: Overdrive: When is it necessary

Originally posted by pony85:<br /> I think what I will end up doing is drive with OD on, to keep the rpms down which should help with mileage right??? I will just control the driving in such a way that I keep the transmission from shifting into OD when I am accelerating etc. Not too hard to do....Plus I just wont use cruise control, since OD kicks in a lot when using that.<br /><br />Bondo- you're right my grandpa is a very smart man. I generaly go to him first with any questions I have about lots of stuff. Someday I hope to be half as knowlegeable as that man

Pony, overdrive is a higher gear; it shifts into OD at cruising speed and downshifts out of OD to accelerate.<br /><br />Otherwise you described what I do...if I'm into hilly country I turn it off cause sometimes it repeatedly shifts, otherwise I run with it on & try not to accelerate enough for a shift if I don't have to. Better mileage that way. It's the shifting that wears out the tranny. <br /><br />and don't worry, you'll be the wise old man someday, if you make it.<br /><br /><br />p.s., check out this really cool site on how automatic transmissions work

 

[Boomyal]

Re: Overdrive: When is it necessary

I won't comment on a particular weight limit for using overdrive in the automatic but here is the main reason not to use it under load. A little detail that no one has mentioned.<br /><br />When the tranny is in overdrive the torque convert is locked. This is the only way that autos could be made to work in overdrive. When the torque converter is locked, it does not allow the circulation of transmission fluid thru it. This set up is engineered to cope with the normal weight of the vehicle.<br /><br />When you add towed weight, the torque converter heats up and can eventually cook even on the flat and level. So my advice is, at least with moderate to heavy weight, keep it in 3rd gear.

 

[jtexas]

Re: Overdrive: When is it necessary

hey boom, that goes against all the other wisdom I've read about...which is that the mechanical link, with TC locked, is superior to the hydraulic link, because the trans fluid doesn't get as hot. just when ya think ya know somethin...<br /><br /><br />for example:<br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=22;t=001436#000000