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Post by erw38 on May 16, 2004 17:06:09 GMT -6
I know the care has one because I have heard numerous people mention it, but where is overdrive and how do I tell if I am using it?
The only thing that I know to look at is if the "D" has a circle around it.
Sorry to appear so stupid, but, what can I say, it comes naturally. ;D
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Post by JimW on May 16, 2004 18:41:18 GMT -6
On your gear shifter, you will notice
P
R N D 3 2 1
OD is essentially D, it puts yout transmission in a lower gearing for higher speeds. Use it a lot, its a good gear.
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dred98
Aurora Driver
Posts: 470
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Post by dred98 on May 16, 2004 18:41:43 GMT -6
As long as you put the transmission in Drive - the D with a circle round it - then the car will switch to overdrive automatically, it's a higher gear than the normal 4th and will save gas when the car is at cruising speed.
Howard
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Post by JimW on May 16, 2004 20:53:02 GMT -6
Howard, what does your tach read at 60 mph in OD? The autobahn gearing forces some really high revs even in OD, if Elan doesnt have Autobahn his tach may not read the same as ours
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dred98
Aurora Driver
Posts: 470
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Post by dred98 on May 17, 2004 16:54:12 GMT -6
I'll check it exactly tomorrow and let you know. Howard
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Post by erw38 on May 17, 2004 18:14:18 GMT -6
You guys confuse me. Another thing. Is it ok to start off in on gear (say 3rd gear) and then switch it into D (overdrive)?
Sorry about all these stupid questions.
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Post by JimW on May 17, 2004 18:56:52 GMT -6
Manually shifting the transmission is not the best practice. If you want to extend the life of the 4T80-E (your tranny) I suggest coming to a complete stop before changing gears. So if you boot around in the city 3rd, even 2nd is ok. But to get into overdrive (before a trip on the freeway, or speeds > 40 mph), wait til you get to a stop light or sign and change your gears.
Your tranny will thank you!
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Post by erw38 on May 17, 2004 20:32:28 GMT -6
Your to technical for me! I am glad you put your tranny in there or else I wound not have had a clue as to what you were talking about. Thanx for the info!
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dred98
Aurora Driver
Posts: 470
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Post by dred98 on May 18, 2004 6:47:28 GMT -6
I checked this morning - (on the way to the dealer to get the A/C fixed) - and 60 mph is just under 2,000 rpm, about 1,900 to 1,950 at a guess. Does this agree with yours?
Howard
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Post by JimW on May 18, 2004 7:14:24 GMT -6
Yeah, that sounds right. I recall in my Bonneville which had a gearing of 2.84, at 100kph (60mph) the tach read 1450-1500. Thanks Howard, k so Elan, you do the same, in Overdrive, I would like to know what your tach reads at 60mph
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Post by erw38 on May 19, 2004 21:40:20 GMT -6
Yes Sir. I will try to find out tomorrow while on the freeway (highway to all you northern folk) because, I am a law abiding citizen.
And of course the local cops do not like people that "push" the speed limit.
Other than that, I'll get right on it Mr. Jim!
Sir, Yes Sir!
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dred98
Aurora Driver
Posts: 470
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Post by dred98 on May 20, 2004 9:30:24 GMT -6
I still don't really understand the difference the axle ratio makes to an Autobahn. I know from my early days with GTO's and Chevelle SS's that a higher ratio gives you more acceleration and quicker 0-60's (In those days we used to measure it 0-100's) So why should the higher ratio give you a higher top speed - isn't that the wrong way round?
Howard
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Post by JimW on May 20, 2004 9:38:56 GMT -6
I'm not suggesting it gives you a higher speed. GTP's and SSEi Bonnevilles are faster then Auroras and they are geard lower. It just revs higher getting up to speed quicker. Overall speed is not a factor, my tach just shows higher revs then my old 89 Bonneville, geared at 2.97:1.
I simply wanted to know the tach reading differences between the 3.48:1 Aurora vs the 3.71:1
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Post by erw38 on May 20, 2004 18:38:33 GMT -6
my tach at 60mph is a hair under 2000rpm........same as Mr. Howards.
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Post by zimaad on Jun 7, 2004 20:03:13 GMT -6
Hope you all have the same tire size. This changes the rpm range too. As does load, HP (for those that have mods), etc. Theoretically, all other things being equal but the drive ratio, the difference is about 7% or maybe 100 +/- RPM.
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Post by JimW on Jun 7, 2004 20:04:55 GMT -6
WIth the classic Aurora yer tire height best not be more then 27.1" or you will fook up yer tranny LARGE
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Post by erw38 on Jun 7, 2004 21:08:56 GMT -6
I am not going to get bigger tires now (for sure)! It's not like I ever was!!!!! ;D ;D ;D to much money for rims and such
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Post by Gary on Mar 29, 2005 10:07:14 GMT -6
:oI'm on your side Howard why call it OD if its D !!! Gary
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Post by Letitroll98 on Mar 29, 2005 11:33:43 GMT -6
Wow, this has to be the dustiest (cough, cough) old thread brought up so far. Funny, it was never answered correctly.
"Overdrive" means that the wheels are being driven at a ratio less than 1:1, giving a faster output speed than the input speed. In other words, your wheels are turning faster than the engine when in overdrive. For comparison 1st gear might be 2.70:1 for fast take off, 2nd 1.55:1, 3rd 1.0:1, and 4th would be overdrive at .79:1 to lower rpm's at crusing speeds. (These ratios are mythical and for example only, but pretty typical) They are achieved by using various combinations of the sun and planetary gearsets.
When in overdrive you will also "lockup" the torque converter. A pin is set in the planetary carrier eliminating any slip in the torque converter giving even better efficiency, re. gas mileage. Putting your car in "Drive" and letting the tranny pick the proper gear will reduce wear and extend the life of your transmission.
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Post by Aurora40 on Mar 29, 2005 14:49:43 GMT -6
Wow, this has to be the dustiest (cough, cough) old thread brought up so far. Funny, it was never answered correctly. "Overdrive" means that the wheels are being driven at a ratio less than 1:1, giving a faster output speed than the input speed. In other words, your wheels are turning faster than the engine when in overdrive. For comparison 1st gear might be 2.70:1 for fast take off, 2nd 1.55:1, 3rd 1.0:1, and 4th would be overdrive at .79:1 to lower rpm's at crusing speeds. (These ratios are mythical and for example only, but pretty typical) They are achieved by using various combinations of the sun and planetary gearsets. When in overdrive you will also "lockup" the torque converter. A pin is set in the planetary carrier eliminating any slip in the torque converter giving even better efficiency, re. gas mileage. Putting your car in "Drive" and letting the tranny pick the proper gear will reduce wear and extend the life of your transmission. Heheh, actually it just means that the output shaft on the tranny is turning more frequently than the input shaft. The differential/axle ratio will affect the overall ratio, and will be somewhere greater than 1:1 Also, it's not uncommon to have torque convertor lockup possible on 3rd and 2nd gear on newer automatics.
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Post by Letitroll98 on Mar 29, 2005 16:49:55 GMT -6
Heheh, actually it just means that the output shaft on the tranny is turning more frequently than the input shaft. The differential/axle ratio will affect the overall ratio, and will be somewhere greater than 1:1 Also, it's not uncommon to have torque convertor lockup possible on 3rd and 2nd gear on newer automatics. Quite right 40man. I was going to say something different than "wheels" to include the final drive ratio (I really do try to simplify and not ramble on), but had to leave the computer and when returning, I just posted it. Thanks for the good lookin' out. I think you multiply by the final drive ratio then divide by the rolling height of the tire? Or something? And yes, for Cafe gas mileage compliances manufacturers are doing everything in their power to increase fuel mileage with lower gear lock ups. Is there any other benefit to locking up the torque converter early, any downside? And do we have a 3rd gear lock up on the 4T80E? I haven't felt it, but I don't really feel much at all from this tranny, what a great design.
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