charm Posted August 9, 2005 Share Posted August 9, 2005 Several years ago I was having a discussion with an ex-gf who had previously dated a mechanic who told her on the street to not drive in the OD gear, but the drive gear. In my auto impreza, that would be 3. What are the pros and cons of driving in the 3 vs D and vice versa? Quote Link to comment Share on other sites More sharing options...
bjwirth Posted August 9, 2005 Share Posted August 9, 2005 I hate when people say "do this or do that" without giving a reason. Next thing you know it's "law." How often should the average driver change their oil? Jiffy lube says it's 3000 miles, so it must be law. But for me the cons would be: lower gas mileage, and louder engine drone. without asking the mechanic, it's hard to know why he said that. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted August 9, 2005 Share Posted August 9, 2005 I hate when people say "do this or do that" without giving a reason. Next thing you know it's "law." How often should the average driver change their oil? Jiffy lube says it's 3000 miles, so it must be law. But for me the cons would be: lower gas mileage, and louder engine drone. without asking the mechanic, it's hard to know why he said that. About the only time I over ride what the auto tranny is doing, is the few times I might be in a line of kinda slow traffic going up a slight grade in hot weather. I might drop it down a gear and let the engine rev a little to keep it from 'lugging'. depends on your tranny, but some will not downshift when it 'seems' they should - so, do it yourself. Again, 99% of the time, the auto is doing what I'd be doing. Carl Quote Link to comment Share on other sites More sharing options...
Scottbaru Posted August 9, 2005 Share Posted August 9, 2005 In a car with overdrive, it'll shift into OD while cruising at fairly low speed, and downshift with every push of the throttle. Around town there's a lot of throttle movement, so a lot of shifting in & out of OD, more wear on the tranny. On most auto trannys with OD, there's usually a separate button to disable OD, or there's both D and OD on the shifter. Normally 3 isn't for typical driving. Quote Link to comment Share on other sites More sharing options...
nipper Posted August 10, 2005 Share Posted August 10, 2005 The only time i've used drive3 is in hilly country, when the car seemed to be shifting an awful lot at highway speed to climb hills. Otherwise i just drive in D. nipper Quote Link to comment Share on other sites More sharing options...
B99Brighton Posted August 10, 2005 Share Posted August 10, 2005 3 will result in lower gas mileage if used all the time. overdrive will be used even at low speeds with a light throttle position. Autos are made to be smarter than you are, so let it do its thing. It will downshift to the correct gear based on a few signals, throttle position, Vehicle speed and load. The later measured bythe map or masf sensor. The computer will then select the right gear for you. Quote Link to comment Share on other sites More sharing options...
RallyKeith Posted August 10, 2005 Share Posted August 10, 2005 Dodge, circa 1990ish, was known for automatics that ate themselves every 20k miles, especially if it had the V6. Reason being, they shifted all the way into over drive as soon as you left off the gas. Then as soon as you pushed back down on the gas pedal it had to downshift back down to the correct gear. This wears things out, and in a hurry. So, american cars have a drive and then overdrive for gear selection. Our subarus have Drive and then third. Our 3rd would be the equivalent to the american drive, highest gear before an overdrive. So if you were to decide to follow this advice then third would be the correct choice. However, from the 3 automatic subarus I've driven (one of each engine size) Subaru really has their $h!t together when it comes to Transmission shifting control. There are no reports of premature transmission failure due to excessive shifting in and out of 4th/OD, and from what I can tell it is very good about waiting to shift into it and back out of it. My vote is keep it in D Keith Quote Link to comment Share on other sites More sharing options...
nipper Posted August 10, 2005 Share Posted August 10, 2005 In the bad old days of lock up torque converters and other oddities, Transmissions didnt have a drive 3 and OD, jusr a D and a 2 and a L. They found out there was driveability issues (thank you GM). This was the 1980's. To solve this issue they added D3 and OD (or D in a circle). The controls were not that advanced back then. The owners manuals would tell you for driving under 40mph use D, and over 40 use OD. Now with computers deciding when to shift into od to some degree, and on some cars doing all the shifting, its no longer necassary. D4/OD/D can be used for everyday driving. Torque converters on some cars lock up in every gear, and you dont even feel it. D3 or D is used for towing, driving up hilly terrane (to keep the car from shifting like mad), or for engine braking. Drive 3 is the 1-2-3 shift. Drive 2 can either be a 1-2 shift (again thanks gm) or a start in second gear, and a forced downshift. Same for 1 or low. Any of these selections can be over ridden by the car at the extreem to protect the engine from over reving. nipper Quote Link to comment Share on other sites More sharing options...
The Dude Posted August 10, 2005 Share Posted August 10, 2005 Over drive simply means that the output shaft of the transmission is turning faster than it's input shaft. PERIOD. Both AT and MT can be overdrive transmissions. Lock up is something different, and only happens in ATs. At lock up the TC goes from inefficient fluid coupling to solid mechanical coupling, like a MT. This is almost always a very good thing. Better mpg. Ineffecient fluid coupling creates heat, the AT killer, lock up greatly reduces the amount of heat generated by your AT. An AT is most inefficient, and generates the most heat, at low speeds or when stopped in gear. Quote Link to comment Share on other sites More sharing options...
nipper Posted August 10, 2005 Share Posted August 10, 2005 True but lockup and OD are used as the same meaning by end users (us) and even technicians. I mean look at motor and engine. motor is electric, engine is mechaical. But its too earlt to get into a discussion about terms. nipper Quote Link to comment Share on other sites More sharing options...
swc7916 Posted August 10, 2005 Share Posted August 10, 2005 In stop and go traffic where the speeds don't exceed 35mph or so, I will put my Outback in 3. I do this so that the transmission won't keep shifting between 3rd and 4th and if I keep it in 3rd I will get the acceleration when I want it, not when the transmission decides to downshift - I hate wanting the car to go but being stuck in too high a gear. Quote Link to comment Share on other sites More sharing options...
charm Posted August 10, 2005 Author Share Posted August 10, 2005 In stop and go traffic where the speeds don't exceed 35mph or so, I will put my Outback in 3. I do this so that the transmission won't keep shifting between 3rd and 4th and if I keep it in 3rd I will get the acceleration when I want it, not when the transmission decides to downshift - I hate wanting the car to go but being stuck in too high a gear. This is how I've been doing it, but my gas mileage is terrible. Although the gas mileage could have something to do with curb I slid into 2 winters ago, I really should get that done. Quote Link to comment Share on other sites More sharing options...
blitz Posted August 10, 2005 Share Posted August 10, 2005 The lockup clutch isn't a huge, robust unit. If it's constantly dis-engaging and re-engaging it will wear out quickly. Use the the 3rd position to prevent it during low-speed, cut & thrust city driving. That's one of the reasons why the selector is there (the other reason is for hill descent control). It cracks me up, folks are afraid to use the gear selector. It's not there for decoration folks. Subaru wouldn't have included it if they didn't intend for it to be used. Use it to REDUCE the amount of needless shifting and braking. Quote Link to comment Share on other sites More sharing options...
Hondasucks Posted August 10, 2005 Share Posted August 10, 2005 I think it also comes from the fact that a lot of Ford transmissions (Namely the E4OD) had weak overdrive bands, so by leaving it in D instead of OD when you are around town, it minimized the amount of time that the overdrive band was used. My ex ALWAYS turned her OD off in her car, and she'd always get mad at her mom cuz when her mom would drive her car she wouldn't take it out of overdrive lol... Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted August 12, 2005 Share Posted August 12, 2005 One more thing is that some AT would overheat in overdrive while towing and thus turning it off has some cooling action: less unlocking of torque converter and more output at the ATF pump. I use 3rd while towing a boat, unless I do 65 mph or more on a freeway. Quote Link to comment Share on other sites More sharing options...
nipper Posted August 12, 2005 Share Posted August 12, 2005 Almost all owners manuals tell you to tow in D3. nipper Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted August 12, 2005 Share Posted August 12, 2005 Almost all owners manuals tell you to tow in D3. nipper Maybe, my subaru's one did not. It only mentioned using 3rd on long uphills. Mind you, the engine does more than 4000 rpm with 70 mpg in 3rd. Quote Link to comment Share on other sites More sharing options...
nipper Posted August 12, 2005 Share Posted August 12, 2005 70 mpg DAMN! hehehhe Odd the manuals I've seen recomend it strongly. Also 70 mph with a trailer (if its a box type trailer) can make life interesting. nipper Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted August 12, 2005 Share Posted August 12, 2005 70 mpg DAMN! hehehhe Odd the manuals I've seen recomend it strongly. Also 70 mph with a trailer (if its a box type trailer) can make life interesting. nipper Dont worry, it tracks perfectly at any speed (it's never empty). Besides, I have brakes on the trailer, it's a boat trailer. Quote Link to comment Share on other sites More sharing options...
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