The Straight Dope

Go Back   Straight Dope Message Board > Main > General Questions

Reply
 
Thread Tools Display Modes
  #1  
Old 10-05-2005, 07:32 AM
black rabbit black rabbit is offline
Guest
 
Join Date: Aug 2000
What's 'drive 2' on an automatic transmission for?

I should probably have to turn in my Man Card after asking this, but it's something that's been bugging me for awhile.

I'm the proud new adoptive parent of an '01 Corolla CE, with the three-speed automatic transmission. Like all of my other previous cars, this one didn't have an owner's manual when I bought it.

I know what drive is for: making the car go forward. I know what low gear is for in a vehicle that's not supposed to be towing anything: better torque on slick, usually snowy roads, especially when you're trying to go uphill without much momentum.

But what the heck is "Drive 2" or "Second Drive" or whatever for? I experimented with it (briefly) while puttering around the side streets on my way out to the interstate this morning, and I didn't notice much difference.

Bonus question: When I want to shift from "drive" to "low," is it better to come to a complete stop, or can I just take my foot off the accelerator and do it? I've always thought for some reason that the various itty bitty peices in an automatic aren't nearly as hardy as a manual clutch, so I should only shift from a stop. My wife counters that I'm a big sissy, and I should shift on the fly. Which is it?
Reply With Quote
Advertisements  
  #2  
Old 10-05-2005, 07:50 AM
TheLoadedDog TheLoadedDog is offline
Guest
 
Join Date: Feb 2001
Unless driving under specific circumstances such as snow or towing a big load on a grade, you put it in Drive and that's that. Set and forget.

Drive2 is like a semi-manual. It will prevent the auto box from seeking a higher gear, but unlike a manual it won't stop it from selecting a lower one.


Don't worry about it. Tell your wife she's wrong, and not to sweat.
Reply With Quote
  #3  
Old 10-05-2005, 08:12 AM
cantara cantara is offline
Guest
 
Join Date: Nov 1999
If it's automatic then it does the shifting for you. In the instance where you want to force a gear, then you can select it on the fly. If you are going fast and bump the lever into 2nd, then the engine will rev up to match the speed of the transmission. I can't think of many situations where you would want to force it back to 2nd, or prevent it from moving to 3rd.

BTW, you can find manuals around if you are interested...
Reply With Quote
  #4  
Old 10-05-2005, 08:17 AM
enipla enipla is offline
Member
 
Join Date: Jul 2001
Location: Colorado Rockies.
Posts: 8,388
Probably the most useful thing '2nd' is for is to slow the vehicle when going down long steep hills. Helps prevent the brakes from over heating.
Reply With Quote
  #5  
Old 10-05-2005, 08:20 AM
Gary T Gary T is offline
Member
 
Join Date: Mar 2002
Location: KCMO
Posts: 9,538
"Drive," on almost any car, means it starts in 1st gear and automatically shifts up. "D" means it shifts up to 3rd gear. "D2" means it shifts up to 2nd gear. Cars with 4-speed automatics use "D4" (e.g. Honda) or "OD" (= overdrive) to indicate shifting up to 4th gear. "1" or "L" (low) means it stays in 1st gear. "2" means it stays in 2nd gear (i.e., it starts out in 2nd gear and stays there).

That's the general rule. I'm sure there are some exceptions, because heaven forbid every car manufacturer did it the same way. For example, years ago Ford had a 3-speed automatic with "D" (regular drive), "D" in a circle (not overdrive -- it started out in 2nd and shifted up to 3rd) and "1."

Downshifting to low gear on the fly runs a risk of breaking something. If you were going 60 mph and selected 1st and it actually engaged 1st at that speed, it could overrev the engine and/or subject the transmission to a heck of a shock load. Generally, automatics are designed so they won't do that -- they don't downshift into the selected gear until a certain compatible road speed is reached. But given the potentially huge expense if something does happen, and the questionable need to shift like that anyway, I wouldn't do it. You don't have to be at a stop, but I'd suggest being at a reasonable speed for the gear selected.
Reply With Quote
  #6  
Old 10-05-2005, 08:33 AM
crazyjoe crazyjoe is offline
Guest
 
Join Date: Dec 2004
Just want to add that even though you put it in "2" on a lot of cars, it WILL shift up to 3rd once you reach a certain RPM level (usually the max reccommended RPM for that vehicle, AKA "the redline").
Reply With Quote
  #7  
Old 10-05-2005, 09:49 AM
black rabbit black rabbit is offline
Guest
 
Join Date: Aug 2000
Just as I suspected. Thanks folks.

However, if I were to do this...

Quote:
Originally Posted by TheLoadedDog
Tell your wife she's wrong, and not to sweat.
...I think I'd risk breaking more than my transmission.
Reply With Quote
  #8  
Old 10-05-2005, 09:51 AM
BobT BobT is offline
Guest
 
Join Date: Mar 1999
I used "2" when driving up and down Mt. Washington in New Hampshire. That's been the only time.
Reply With Quote
  #9  
Old 10-05-2005, 12:44 PM
AHunter3 AHunter3 is offline
Charter Member
 
Join Date: Mar 1999
Location: NY (Manhattan) NY USA
Posts: 16,298
You aren't putting appreciably more wear and tear on an automatic transmission when you shift from D to 2 (or S, some manufacturers put "S" to mean the same thing), or, for that matter, to "L" or "1".

The automatic transmission lever switches a valve to a position that no longer lets the pressurized hydraulic fluid move the valves & whatnot to a position that lets the tranny upshift.

GaryT:
Quote:
Downshifting to low gear on the fly runs a risk of breaking something. If you were going 60 mph and selected 1st and it actually engaged 1st at that speed, it could overrev the engine and/or subject the transmission to a heck of a shock load.
If it is safe to do so (determined within the tranny by the existing pressures which in turn are a product of speed @ current gear), the tranny will drop to the requested gear (from 3rd or higher to 2nd in the case of "2" or "S", or from 2nd or higher to 1st in the case of "1" or "L"); otherwise, if the existing pressure mandates otherwise (meaning the speed is too high in the current gear to downshift), it won't. Abruptly throwing your gearshift lever into "L" at 110 MPH will not cause your transmission to switch to 1st gear unless something is badly wrong with your transmission.

crazyjoe:
Quote:
Just want to add that even though you put it in "2" on a lot of cars, it WILL shift up to 3rd once you reach a certain RPM level (usually the max reccommended RPM for that vehicle, AKA "the redline").
I'm not going to call you "wrong" but it should not do so (IMHO) and I've never used an auto-tranny car that did so. The main purpose of the lower gear-settings is specifically to prevent such an upshift, using the engine compression as a means of limiting the automobile speed. It's useful when descending hills and useful in slippery conditions. Also useful in some heavy-traffic conditions when you want feather-touch responsiveness from the accelerator, to accelerate and decelerate in very tiny amounts, e.g., while merging, etc.

You could do damage to a vehicle by putting it in "L" and flooring it and running the engine way out beyond the red line, but you could also do such damage by putting it in "D" and accelerating to way out beyond red line in high gear (it just takes longer). You're far less likely to damage your engine (or tranny) by putting the vehicle in "L" or "S" and having the weight of the vehicle descending the hill force it to a speed beyond what it was intended to run at in that gear, and generally if you were in such a situation that might well be the lesser of two evils anyhow.
__________________
Disable Similes in this Post
Reply With Quote
  #10  
Old 10-05-2005, 12:56 PM
CookingWithGas CookingWithGas is offline
Charter Member
 
Join Date: Mar 1999
Location: Tysons Corner, VA, USA
Posts: 9,776
Quote:
Originally Posted by black455
I know what low gear is for. . .: better torque on slick, usually snowy roads, especially when you're trying to go uphill without much momentum.
Slightly off topic but when the road is slick you don't want more torque, you're more likely to spin wheels.

An auto tranny will automatically downshift if you get on the gas, giving you more power such as for passing or going up a steep hill. You can get that power by dropping to 2, although as mentioned, watch the RPMs. You don't have to stop any more than you would have to stop if driving a stick.

Quote:
Originally Posted by AHunter3
. . .you could also do such damage by putting it in "D" and accelerating to way out beyond red line in high gear (it just takes longer).
How many production cars with auto trannies can actually pull redline in D, especially when most of them have overdrive now?
Reply With Quote
  #11  
Old 10-05-2005, 01:02 PM
enipla enipla is offline
Member
 
Join Date: Jul 2001
Location: Colorado Rockies.
Posts: 8,388
Quote:
Originally Posted by CookingWithGas
Slightly off topic but when the road is slick you don't want more torque, you're more likely to spin wheels.
Correct.

A lower gear will be more likely to cause you to lose traction/spin your wheels.

Some people think that a lower gear somehow gives you more traction. Thatís just not the case. It has nothing to do with it.
Reply With Quote
  #12  
Old 10-05-2005, 04:37 PM
AHunter3 AHunter3 is offline
Charter Member
 
Join Date: Mar 1999
Location: NY (Manhattan) NY USA
Posts: 16,298
I'm a fossil from the era of rear-wheel drive vehicles. A lower gear in icy or wet conditions meant that you could use engine drag to slow the car safely, putting smooth and continuous resistance to the rear wheels while the steering (front) wheels remained responsive. In contrast, if you tried to slow the vehicle by tapping the brakes, you ran the risk of losing steering (the front wheels partially or fully skidding = not much response to sterring) or fully breaking the car loose (hitting brakes too hard, hydroplaning or skating)

It's of considerably less use with front wheel drive cars, and aside from that brakes work better than they used to.
Reply With Quote
  #13  
Old 10-05-2005, 05:05 PM
CynicalGabe CynicalGabe is offline
Guest
 
Join Date: Nov 2004
Leave your Man Card at the desk on the way out.
Reply With Quote
  #14  
Old 10-05-2005, 06:07 PM
kanicbird kanicbird is offline
Guest
 
Join Date: May 1999
Depending on the tranny:

- will place the car in 1 or 2, used when the tranny shifts between 2-3 multiple times due to the speed you are traveling. going down hill and want to use engine braking, or want to place the car in a lower gear manually for situations which require it (passing, getting by school buses before then turn on those dreaded red flashing lights).

or

Will lock the car in 2nd gear, which can be used in the above, but also allow you to start from a stop in 2, which is helpful sometimes on ice or snow.
Quote:
Just want to add that even though you put it in "2" on a lot of cars, it WILL shift up to 3rd once you reach a certain RPM level (usually the max reccommended RPM for that vehicle, AKA "the redline").
Also all the cars I have driven will NOT override this, if you excede the redline it will either let you or engage a rev limiter, it will NOT shift you into 3rd. You COULD damage your car if you exect it to.


Quote:
Downshifting to low gear on the fly runs a risk of breaking something.
Only if you are exceding the redline, All AT''s I know of are not only able to be downshifted on the fly, and designed to be able, if you excede the redline you do, this could happen just as easially with a stick shift.
Reply With Quote
  #15  
Old 10-05-2005, 07:00 PM
enipla enipla is offline
Member
 
Join Date: Jul 2001
Location: Colorado Rockies.
Posts: 8,388
Quote:
Originally Posted by kancibird
Will lock the car in 2nd gear, which can be used in the above, but also allow you to start from a stop in 2, which is helpful sometimes on ice or snow.
Huh. Are you sure? I've never seen this. I thought that in all automatics, if you put it in second, it will still start moving using first, and won't shift into third.

You said 'Depending on the tranny'. Do you know what manufacturers do this?

Quote:
Originally Posted by kancibird
Also all the cars I have driven will NOT override this, if you excede the redline it will either let you or engage a rev limiter, it will NOT shift you into 3rd. You COULD damage your car if you exect it to.
I've never seen a car overide this either.

Another reason you may want to use 2nd, or turn off overdrive is when the transmission continues to shift between the two and can't find it's 'sweet spot'. Typical when pulling a long hill/mountain pass.

Good info on automatics - Howstuffworks
Be prepared to take notes. 18 pages worth of diagrams and explaination.
Reply With Quote
  #16  
Old 10-05-2005, 07:10 PM
Mr. Slant Mr.  Slant is offline
Guest
 
Join Date: Nov 2001
Quote:
Originally Posted by CookingWithGas
SNIP
How many production cars with auto trannies can actually pull redline in D, especially when most of them have overdrive now?
If you mean "D" instead of "OverDrive" then quite a few.
A lot of relatively modern cars hit their top speed by going: 1, top of 1st, 2, top of 2, 3, top of 3, middle of 4th, top speed a few thousand RPM below top of 4th.
A bunch of cars can do that. What makes it far from universal is the fact that many carmakers will artificially limit a car's top speed in order to use cheaper tires on it.
My 2002 Mercury Sable can probably top 130, but it's been governed to right around 108. That lets Ford give it tires rated for 112, which are $50 or more per rim cheaper than tires rated for 149.
My 1996 Chevy Caprice had a certifiable stop speed just under 140, but was similarly governed to right around 108, likely for similar reasons. The same vehicle in police trim or "sporty" trim as a 1996 Impala would happily break 135.

In my Caprice, "2" meant to use 2nd gear. No 1st gear, no 3rd. I never tried flooring it and going to the top of 2nd to see if it moved to 3rd. 2nd gear was particularly useful in traffic, parades or funeral processions, as it decreased your torque to the rear wheels and allowed you to spend less time pushing down hard on the brake pedal. It would also have been handy for purposes of starting out on ice or snow without spinning my wheels, although I only used it for that four times per winter.

Regarding shifting down to 1 or 2 when attempting to slow your car on ice or snow... try not to. I gigitygitygity near wound up doing a 180 one time when I did that. If your traction's bad enough, the downshift may apply TOO MUCH braking.
Reply With Quote
  #17  
Old 10-05-2005, 08:12 PM
enipla enipla is offline
Member
 
Join Date: Jul 2001
Location: Colorado Rockies.
Posts: 8,388
Quote:
Originally Posted by Mr. Slant
In my Caprice, "2" meant to use 2nd gear. No 1st gear, no 3rd. I never tried flooring it and going to the top of 2nd to see if it moved to 3rd. 2nd gear was particularly useful in traffic, parades or funeral processions, as it decreased your torque to the rear wheels and allowed you to spend less time pushing down hard on the brake pedal. It would also have been handy for purposes of starting out on ice or snow without spinning my wheels, although I only used it for that four times per winter.
Never knew that. I always though that 2nd would prevent 3rd but not 1st. You and Kancibird agree on this.

I drive manuals, mostly. Iíll have to try that in my Wifes Grand Jeep. Should be easy enough to feel the difference between 2nd and 1st.

Itís pretty tricky. We drive 4x4s. Itís not unusual to need to go into low range (not just Ďfirstí) in deep snow (one foot or more). While this provides a great deal more tourqe to the wheels, and can cause the wheels to break free. Sometimes, itís the only way to provide enough power to keep the vehicle moving through it without bogging down.

Quote:
Originally Posted by Mr. Slant
Regarding shifting down to 1 or 2 when attempting to slow your car on ice or snow... try not to. I gigitygitygity near wound up doing a 180 one time when I did that. If your traction's bad enough, the downshift may apply TOO MUCH braking.
Oh yeah. Also, bad news if you are going uphill on an icy road and the tranny desides it wants a lower gear.

Surprise. Zingo..
Reply With Quote
  #18  
Old 10-05-2005, 09:27 PM
SmackFu SmackFu is offline
Guest
 
Join Date: Sep 2000
Quote:
Originally Posted by AHunter3
A lower gear in icy or wet conditions meant that you could use engine drag to slow the car safely, putting smooth and continuous resistance to the rear wheels while the steering (front) wheels remained responsive. In contrast, if you tried to slow the vehicle by tapping the brakes, you ran the risk of losing steering (the front wheels partially or fully skidding = not much response to sterring) or fully breaking the car loose (hitting brakes too hard, hydroplaning or skating)
I still use mine for that in my front-wheel drive car. In bad conditions, it's the only way I can get down the steep hill near my house and still stop at the stop sign at the bottom.
Reply With Quote
  #19  
Old 10-05-2005, 09:58 PM
CookingWithGas CookingWithGas is offline
Charter Member
 
Join Date: Mar 1999
Location: Tysons Corner, VA, USA
Posts: 9,776
Quote:
Originally Posted by Mr. Slant
If you mean "D" instead of "OverDrive" then quite a few.
I don't know about you but in every automatic I've ever driven, you put it in D and the car decides when to go to OD, not me. (Unless you push the OD Release button so it doesn't, which I guess most have now.) In any case I meant overdrive.

Quote:
2nd gear was particularly useful in traffic, parades or funeral processions, as it decreased your torque to the rear wheels . . .
Oh, there's that torque thing again. Downshifting increases torque, but decreases speed.
Reply With Quote
  #20  
Old 10-06-2005, 12:10 AM
Rick Rick is offline
Charter Member
 
Join Date: Aug 1999
Posts: 15,697
Quote:
Originally Posted by enipla
Huh. Are you sure? I've never seen this. I thought that in all automatics, if you put it in second, it will still start moving using first, and won't shift into third.

You said 'Depending on the tranny'. Do you know what manufacturers do this?
Volvos for one.
If you place the trans in winter mode (Push the W button) when in position D the car will make a 3rd gear start and then shif to fourth. If you place the shifter position 2 the car will start and stay in 2, if you place the shifter in 1 it will start and stay in 1.

Quote:
Originally Posted by Gary T
Downshifting to low gear on the fly runs a risk of breaking something. If you were going 60 mph and selected 1st and it actually engaged 1st at that speed, it could overrev the engine and/or subject the transmission to a heck of a shock load.
I hate to disagree with Gary T, but I have never seen a trans that will downshift and over rev an engine. In this I include the units I drove when I was young and dumb, and did many a stupid thing. I never had an engine over rev. Nowadays with electronic controls, the electronics won't let you do something stupid. For example to demonstrate to my students that the control unit really does protect the driver from stupid mistakes, I will place the selector into R when going oh say 50mph forward Result? nothing, the trans just stays goes to N and stays there.
Reply With Quote
  #21  
Old 10-06-2005, 04:59 AM
Gary T Gary T is offline
Member
 
Join Date: Mar 2002
Location: KCMO
Posts: 9,538
Quote:
Originally Posted by Gary T
Downshifting to low gear on the fly runs a risk of breaking something. If you were going 60 mph and selected 1st and it actually engaged 1st at that speed, it could overrev the engine and/or subject the transmission to a heck of a shock load.
I admit that this was more of a theoretical proposition, along the lines of "why would you want to do such a thing?" Please note the bolded passage.

Quote:
Generally, automatics are designed so they won't do that -- they don't downshift into the selected gear until a certain compatible road speed is reached.
Somehow this part seems to have been overlooked.

The original question asked about "drive 2," not about "2." The word "drive" implies automatic shifting of two or more gears, not selection of only one gear. If it's labeled "D2," I think it's safe to say it will start in 1st and shift to 2nd. It will not shift higher than that. If it's labeled "2," it probably engages only 2nd, though it wouldn't surprise me if on some cars it starts in 1st and shifts to 2nd.
Reply With Quote
  #22  
Old 10-06-2005, 07:09 AM
Dog80 Dog80 is offline
Guest
 
Join Date: Dec 2003
Just wondering: most new automatic cars in Europe have 5 to 7 gears and sequential shifting. Some cars (Alfa Romeo comes to mind) even have paddles behind the steering wheel. Yet, in this forum I keep hearing about 3 and 4 gear cars. Aren't those features available in the US yet?
Reply With Quote
  #23  
Old 10-06-2005, 07:35 AM
Gary T Gary T is offline
Member
 
Join Date: Mar 2002
Location: KCMO
Posts: 9,538
Quote:
Originally Posted by Dog80
Just wondering: most new automatic cars in Europe have 5 to 7 gears and sequential shifting. Some cars (Alfa Romeo comes to mind) even have paddles behind the steering wheel. Yet, in this forum I keep hearing about 3 and 4 gear cars. Aren't those features available in the US yet?
Yes, but 99% of the cars on the road don't have them.
Reply With Quote
  #24  
Old 10-06-2005, 08:27 AM
Mr. Slant Mr.  Slant is offline
Guest
 
Join Date: Nov 2001
Quote:
Originally Posted by CookingWithGas
I don't know about you but in every automatic I've ever driven, you put it in D and the car decides when to go to OD, not me. (Unless you push the OD Release button so it doesn't, which I guess most have now.) In any case I meant overdrive.

Oh, there's that torque thing again. Downshifting increases torque, but decreases speed.
Re: gear D versus OD, my last 4 cars have had gear select indicators for both OD and D.
These cars:
2002 Mercury Sable: OD, D, 1
1996 Chevrolet Caprice Classic: OD, D, 2, 1
1993 Oldsmobile 98: OD, D, can't remember if it had 2, 1
1992 Mercury Grand Marquis: OD, D, can't remember what if had below D. I know it had something.

The car before that was a 4-speed stick.
The car before that was a 1977 Ford LTD. It had a 3-speed automatic, so it just had D, 2, and 1.

I know what you're talking about, though. I suppose if you look back, you could make a list of cars across the years that used the push-button overdrive toggle, explaining the fact that you've never seen cars like most of mine.
I had a rental 2002 Ford Escape, and it had a little toggle button to enable or disable overdrive. I also drove a Honda CRV with that feature.

In case you misread, I used the selection of gear 2 to force my Caprice to shift the car UP to 2nd gear from 1st while I was idling it or operating it at speeds under 10 miles per hour. This would prevent it from trying to idle at 9 MPH in D, and keep the wear down on my knee and legs at the McDonald's drive-thru or similar situations.
Reply With Quote
  #25  
Old 10-06-2005, 08:40 AM
Gary T Gary T is offline
Member
 
Join Date: Mar 2002
Location: KCMO
Posts: 9,538
All automatic transmission cars with overdrive (= 4th gear) have a way to select drive (automatic shifting) without going into 4th. On some, there's a choice between "OD" (4-speed drive) and "D" (3-speed drive), others have only "D" and there's an overdrive-off switch to disable 4th (both types have been mentioned above). Different car makers seem determined to find and use different patterns of gear selection and different ways to indicate same. If you want to know how it's laid out on your car, check the owner's manual.
Reply With Quote
  #26  
Old 10-06-2005, 09:01 AM
crazyjoe crazyjoe is offline
Guest
 
Join Date: Dec 2004
Quote:
Originally Posted by enipla

I've never seen a car overide this either.
You guys don't drive Chryslers, do you?

I've driven them nearly exclusively in my lifetime, and I quite distinctly remember my dad (who is a Chrysler mechanic in the powertrain components dept) showing me that even if you put it in the lower gear, if you run it to the redline, it will upshift out of your current gear and into a higher one. Iy my current car wasn't an autostick, I'd go out and try it this afternoon on my lunch break. The autostick, however, is a slightly different computer controlled version of the automatic, and it definitely will shift up if you leave it in one selection till the redline.

One of the reasons for keeping the selector in the lower gear is that if you leave it in "D" and floor it, on some cars, it will upshift before the redline, and when drag racing (on an approved track, etc etc) some people want to go all the way to the redline before the shift.
Reply With Quote
  #27  
Old 10-06-2005, 09:17 AM
CookingWithGas CookingWithGas is offline
Charter Member
 
Join Date: Mar 1999
Location: Tysons Corner, VA, USA
Posts: 9,776
Quote:
Originally Posted by Mr. Slant
In case you misread, I used the selection of gear 2 to force my Caprice to shift the car UP to 2nd gear from 1st while I was idling it or operating it at speeds under 10 miles per hour. This would prevent it from trying to idle at 9 MPH in D, and keep the wear down on my knee and legs at the McDonald's drive-thru or similar situations.
Hmmm. I may have misread, although another phrase that fed into my interpretation, which I didn't quote, is "allowed you to spend less time pushing down hard on the brake pedal." Going into 2nd as opposed to 1st wouldn't allow to spend less time on the brakes but more. So I assumed you were talking about 2nd as opposed to D.
Reply With Quote
  #28  
Old 10-06-2005, 12:29 PM
SmackFu SmackFu is offline
Guest
 
Join Date: Sep 2000
Quote:
Originally Posted by Dog80
Just wondering: most new automatic cars in Europe have 5 to 7 gears and sequential shifting.
I thought people in Europe didn't have automatic transmissions?
Reply With Quote
  #29  
Old 10-06-2005, 01:04 PM
Mr. Slant Mr.  Slant is offline
Guest
 
Join Date: Nov 2001
Quote:
Originally Posted by CookingWithGas
Hmmm. I may have misread, although another phrase that fed into my interpretation, which I didn't quote, is "allowed you to spend less time pushing down hard on the brake pedal." Going into 2nd as opposed to 1st wouldn't allow to spend less time on the brakes but more. So I assumed you were talking about 2nd as opposed to D.
I suspect you're thinking of using to 1 to SLOW the car from higher speeds.
I'm trying to refer to using 2 to keep the car from REACHING higher speeds.. or any speed at all.
Let's look at hypothetical car similar to a 1996 Chevy Impala SS with a Gear 1 with a ratio of 3.06 and a Gear 2 with a ratio of 1.63. The calculated torque curve on this engine shows that at an 800 RPM idle it makes in the vicinity of 150 ft-lbs of torque.
After all of the calculations for tire size and gear ratios are completed, the car is capable of providing 1050 ft-lbs of torque to the rear wheels if it were at full throttle, and likely around 250 ft-lbs of torque or so at an idle throttle setting.
At this setting, holding it still using the brakes is a little bit tiring.
With Gear 2 active, you wind up with a full-throttle capacity for 545 ft-lbs at the wheels, and a likely delivery of 136 ft-lbs of torque to the rear wheels at an idle throttle setting.
In Gear 2, I will only have to apply 54% of the braking I would have to have applied in Gear 1 to keep the vehicle stationary.
If I did the numbers for Gears 3 and 4 (which I can't force that car into at a stop) you'd see even lower torque numbers.
The above calculations assume that the vehicle makes 25% of peak torque at idle. This assumption is based on my readings of certain on-board diagnostics tools on a number of vehicles, but is still a shaky conclusion. However, regardless of the value plugged in where I used 25%, the relative torque numbers would wind up being the same.
Reply With Quote
  #30  
Old 10-06-2005, 01:08 PM
Mr. Slant Mr.  Slant is offline
Guest
 
Join Date: Nov 2001
Amend
"After all of the calculations for tire size and gear ratios are completed, the car is capable of providing 1050 ft-lbs of torque to the rear wheels if it were at full throttle, and likely around 250 ft-lbs of torque or so at an idle throttle setting."
to
"After all of the calculations for tire size and gear ratios are completed, in Gear 1 the car is capable of providing 1050 ft-lbs of torque to the rear wheels if it were at full throttle, and likely around 250 ft-lbs of torque or so at an idle throttle setting."

Dang. Sorry. I blame my dog.
Reply With Quote
  #31  
Old 10-06-2005, 01:10 PM
Mr. Slant Mr.  Slant is offline
Guest
 
Join Date: Nov 2001
Quote:
Originally Posted by SmackFu
I thought people in Europe didn't have automatic transmissions?
He never said most Europeans had automatic transmissions, just that of European cars with automatic transmissions, have fancy-pants shifting and gobs of gears.
Reply With Quote
  #32  
Old 10-06-2005, 01:41 PM
Dog80 Dog80 is offline
Guest
 
Join Date: Dec 2003
Quote:
Originally Posted by SmackFu
I thought people in Europe didn't have automatic transmissions?
There are automatic transmission cars in Europe, but the percentage is really low. I guess it is similar to the percentage of stick-shift cars in the US.
Reply With Quote
  #33  
Old 10-06-2005, 04:59 PM
wolfstu wolfstu is offline
Charter Member
 
Join Date: Jan 2001
Location: Earth
Posts: 1,657
Quote:
Originally Posted by Rick
Nowadays with electronic controls, the electronics won't let you do something stupid. For example to demonstrate to my students that the control unit really does protect the driver from stupid mistakes, I will place the selector into R when going oh say 50mph forward Result? nothing, the trans just stays goes to N and stays there.
This is certainly not the case for all vehicles. I've been in both a Pontiac Montana and a Chevrolet Express 2500 that, while moving down the road at 90 (Montana) or 40 (Express) km/h, could be shifted from D into R. In both cases the result was a sudden engine stall (as might be expected), and in both cases the engine restarted when N was selected and the starter engaged. The Montana was of the 2003 model year (give or take) and the Express was a 2005.

Further, I've been in a 1984 Chevrolet Cavalier in which it was possible to shift from D to 2, then subsequently to 1 while going about 80 km/h down a steep hill. The result was a very high-speed and noisy revving of the engine until the 2 was again selected.


So maybe it's just GM, but not all cars are smart enough to keep you from putting the gear selector in the wrong place.



(If anybody's curious, the Montana was a passenger playing a trick on the driver, the Express was the driver aiming for neutral and overshooting, and the Cavalier was the driver tyring to see if the car would do it. wolfstu does not recommend stalling the engine out at highway speeds; both power brakes and steering become inactive.)
Reply With Quote
  #34  
Old 10-06-2005, 07:05 PM
kanicbird kanicbird is offline
Guest
 
Join Date: May 1999
Quote:
The autostick, however, is a slightly different computer controlled version of the automatic, and it definitely will shift up if you leave it in one selection till the redline.
Well not on subies (Subarus). If you hit the redline on a a/t 'sports shift', the rev limiter will engage, it will NOT shift you to the next gear. It will however downshift you back to 1st when you slow to a stop (you can start in 2nd if you want, but you must manually put it into 2nd). In 'sports fully auto' mode it will take you to redline before shifting under heavy acceleration - but that is fully auto mode. (there is 3 drive modes - normal a/t, sports a/t and sports shift 'manumatic').
Reply With Quote
  #35  
Old 10-06-2005, 10:10 PM
Rick Rick is offline
Charter Member
 
Join Date: Aug 1999
Posts: 15,697
Quote:
Originally Posted by wolfstu
This is certainly not the case for all vehicles. I've been in both a Pontiac Montana and a Chevrolet Express 2500 that, while moving down the road at 90 (Montana) or 40 (Express) km/h, could be shifted from D into R. In both cases the result was a sudden engine stall (as might be expected), and in both cases the engine restarted when N was selected and the starter engaged. The Montana was of the 2003 model year (give or take) and the Express was a 2005.

Further, I've been in a 1984 Chevrolet Cavalier in which it was possible to shift from D to 2, then subsequently to 1 while going about 80 km/h down a steep hill. The result was a very high-speed and noisy revving of the engine until the 2 was again selected.


So maybe it's just GM, but not all cars are smart enough to keep you from putting the gear selector in the wrong place.



(If anybody's curious, the Montana was a passenger playing a trick on the driver, the Express was the driver aiming for neutral and overshooting, and the Cavalier was the driver tyring to see if the car would do it. wolfstu does not recommend stalling the engine out at highway speeds; both power brakes and steering become inactive.)
OK, can I amend my answer to on real cars the computer won't let you do anything stupid?
(Ducks and runs like hell)
As Gary T said upthread a bit, God forbid that all the car makers do it the same way.
Reply With Quote
  #36  
Old 10-07-2005, 06:01 AM
Liberal Liberal is offline
Guest
 
Join Date: Nov 1999
I hope it's appropriate to ask this question here. It's closely related, and I'd hate to burden he forum with two threads.

Somehow, our Saturn Ion (2003) gears correctly in hilly and mountainous driving. We can leave it in D, and going downhill, you can "feel" the car holding the gear and not shifting up. It will not shift up until the car has leveled off. I don't know whether it senses the incline or what. Does anyone know how the car does this?
Reply With Quote
  #37  
Old 10-07-2005, 06:25 AM
Pushkin Pushkin is offline
Guest
 
Join Date: Oct 1999
Quote:
Originally Posted by enipla
Never knew that. I always though that 2nd would prevent 3rd but not 1st. You and Kancibird agree on this
While waiting for my g/f to finish a doctor's appointment, I read up the car's manual (I was bored and forgot a paper or book) If an automatic version, the gearbox's "2" option would hold it in 2nd gear and 2nd gear only. It also had D1-D4 (Honda Civic) that would do the same with other gears and it was also suggested the car could be driven as a semi-automatic simply by pushing up and down through D1-D4. This "semi-automatic" mode IIRC was frowned upon by other Dopers in a thread quite some time ago.
Reply With Quote
  #38  
Old 10-07-2005, 06:30 AM
Pushkin Pushkin is offline
Guest
 
Join Date: Oct 1999
Quote:
Originally Posted by Dog80
Just wondering: most new automatic cars in Europe have 5 to 7 gears and sequential shifting. Some cars (Alfa Romeo comes to mind) even have paddles behind the steering wheel. Yet, in this forum I keep hearing about 3 and 4 gear cars. Aren't those features available in the US yet?
IMO most cars in Europe would have smaller engines and be designed with frugality in mind. More gears mean more economy and are handy for squeezing more performance out of the engine. If you have a large V6 or V8 and have cheap fuel, you don't have to worry so much about how many gears you have. All the same, I would have thought more than 5 automatic gears would still have been the preserve of more expensive motors.
Reply With Quote
  #39  
Old 10-07-2005, 07:15 AM
Rick Rick is offline
Charter Member
 
Join Date: Aug 1999
Posts: 15,697
Quote:
Originally Posted by Liberal
I hope it's appropriate to ask this question here. It's closely related, and I'd hate to burden he forum with two threads.

Somehow, our Saturn Ion (2003) gears correctly in hilly and mountainous driving. We can leave it in D, and going downhill, you can "feel" the car holding the gear and not shifting up. It will not shift up until the car has leveled off. I don't know whether it senses the incline or what. Does anyone know how the car does this?
If I am understanding you correctly, Volvo did that for a few years back in the early 90s. When going downhill, and the trans was set in ecomony mode if the trans control unit saw the speed increasing, it downshifted to 3rd to allow engine braking. This was done to help make the brake pads last longer.
Customers did not understand the function, complained, and it was removed a few years later.
Reply With Quote
  #40  
Old 10-07-2005, 08:17 AM
kanicbird kanicbird is offline
Guest
 
Join Date: May 1999
Quote:
D into R. In both cases the result was a sudden engine stall (as might be expected), and in both cases the engine restarted when N was selected and the starter engaged.
Yes there is a stall converter which would stop the engine if the tranny speed and engine speed were too far apart for too long. In one shop manual I had (forgot which car) it gave a way to test the stall converter. IIRC it was to block all wheels, set the E-brake fully, fully apply the service brake, and place the car so that forward movement would not cause harm (like a big empty field, or the front bumper up against a old growth oak tree. Then place the selector in 1 and, well basically floor it till a certain rpm's were reached and hold it there for a certain amount of time, the engine should stall out if the stall converter was working.
Reply With Quote
  #41  
Old 10-07-2005, 09:44 AM
Pushkin Pushkin is offline
Guest
 
Join Date: Oct 1999
One of the Google ads is entitled "Learn Stick Shift", I just thought (automatically ) what other way is there to drive. In the UK you can take your driving test in an automatic car, but if you want to drive a manual you need to take the test, again, in a manual vehicle.
Reply With Quote
  #42  
Old 10-07-2005, 10:21 AM
Dog80 Dog80 is offline
Guest
 
Join Date: Dec 2003
Quote:
Originally Posted by Pushkin
IMO most cars in Europe would have smaller engines and be designed with frugality in mind. More gears mean more economy and are handy for squeezing more performance out of the engine. If you have a large V6 or V8 and have cheap fuel, you don't have to worry so much about how many gears you have. All the same, I would have thought more than 5 automatic gears would still have been the preserve of more expensive motors.
Cars like BMW X5, Porsche Cayenne and Volkswagen Tuareg have 6 and 7 gear auto trannies.
Reply With Quote
  #43  
Old 10-07-2005, 11:06 AM
Mr. Slant Mr.  Slant is offline
Guest
 
Join Date: Nov 2001
Quote:
Originally Posted by Rick
If I am understanding you correctly, Volvo did that for a few years back in the early 90s. When going downhill, and the trans was set in ecomony mode if the trans control unit saw the speed increasing, it downshifted to 3rd to allow engine braking. This was done to help make the brake pads last longer.
Customers did not understand the function, complained, and it was removed a few years later.
Did this tranny also have Sport & Normal modes?
If so, what would it have done in those modes in the same situation?
I'm glad to see an automaker validating my long-standing belief that as long as engine braking adds up to the transfer of less power than my engine uses to make the car go FORWARD at 70 MPH, the engine braking poses no substantial risk to the transmission.
Reply With Quote
Reply



Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 06:20 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright © 2013 Sun-Times Media, LLC.