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2007 isuzu ascender
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Discussion Starter · #1 ·
I've seen where you guys use 3rd for city driving when you have the overdrive option, but how do I know if my vehicle actually has the Overdrive option? I dont have the O shadowed outside of the D on my shifter, so does that mean it's not overdrive? I do have gears 1,2,3,D though.... Can anyone give me some insight?
 

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2007 chevy trailblazer_lt
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You have OD more or less. 4th gear as it were. If you don't want to use it, put her in "3", but if you a doing packed in slow speeds, you will probably never hit 4th anyway. If you do some highway or open road driving, 4th will give you better fuel economy. Just use Drive.
 

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Discussion Starter · #3 ·
OK I guess I was just asking if it was better to use 3rd instead of OD during city driving. If it was better fuel economy, better for the vehicle, etc... I've been told by a couple people that they always drive in 3rd and it's better for the vehicle, and they only use Drive or "OD" for the highway.
 

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I turn of stabilitrac and overdrive...hold the bottom button under the shifter for about 6 seconds.....it'll blink and stay lit..........shift it in 3rd and your good to go........the only time I put it in drive is when I am on the highway!!
 

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2009 chevy
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The simple answers is this: in the days of the dumb engine control computer, the trucks did not have the smarts to select the proper gear. It was better to manually select the 1:1 ratio gear for slow speed driving.
Today, the powertrain control module is smarter than we are. Put it in D (the overdrive position) and let the computer select the ratio. :thumbsup:
 

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2005 chevy trailblazer_ls_ext
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I have to respectfully disagree. In my case my morning commute consists of about 4 - 5 miles of stop and going driving, the highest MPH being about 45 though most of it is about 35 - 40.

If I put my EXT (or any other vehicle) in Drive (overdrive) yes the PCM will allow the transmission to shift into fourth gear and engage the torque converter lock up clutch right around 40 MPH.

Yes the RPMs drop way down. BUT . . .
if traffic suddenly slows down, or I don't make the light, or need to accelerate, it downshifts to third gear. This can happen several times. I can't see what benefit there is from the transmission shifting back and forth from third to fourth. Actually quit the contrary I think it COULD shorten the life of the transmission considerably. I figure any transmission has X amount of shifts in it, so why waste them? For me it's just as easy to put it into "3" when I leave the house.

Of course if I know I'm going to driving on a freeway or highway then it's a no brainer!

I have done this in one of my other vehicles (non GM) and the tranny has over 200K miles on it. Personally I don't think the transmissions in these vehicles are a strong point - if you don't believe me ask Spong or anyone else who has had them fail at low mileage.
 

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2009 chevy
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I have to respectfully disagree.

Personally I don't think the transmissions in these vehicles are a strong point - if you don't believe me ask Spong or anyone else who has had them fail at low mileage.
Super, i just happen to be in here when you posted.

You can disagree all you like, my friend; and you don't even need to be respectful :raspberry. See, I'm not :D.

Of course, all situations are different, if 3 works for you and your commute, go for it.

BTW, I agree with your opinion of the transmissions :thumbsup:
 

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2003 chevy trailblazer_ls
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In city driving, it is not a matter of parts wear, etc., but rather gear ratio and if the vehicle is shifting up into OD and lugging (too low an RPM).

I have oversized tires with 3.73 gears and often find my city RPMs at under 1200. That is barely off idle. Better to use 3 and rev up a bit more.

And, no, our "smart" PCM-controlled cars will not select the proper ratio. They just shift at set points determined by throttle position and load requirements. They will indeed shift into OD if conditions are right, even if the engine is barely turning over.

One thing that I wonder about with a lot of these posts is why people are so afraid to try something new or different with their vehicles, but that is probably a side discussion for a different thread. Just try it in 3 and see if you like it (if the vehicle responds well). If so, use it. If not, don't. No big deal...
 

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And, no, our "smart" PCM-controlled cars will not select the proper ratio. They just shift at set points determined by throttle position and load requirements. They will indeed shift into OD if conditions are right, even if the engine is barely turning over.
The reason, of course, that the PCM does this is because it has been programmed for the highest economy.

And, I'm not interested in debating the subject, but if you compare today's PCM programing with a vehicle from the '80s, you would call today's PCMs "smart". The problem is in the definition of the proper ratio.

The PCM has the ability to learn driving habits (and that, by the way, is what makes it a smart computer); some of us are happy with the way the PCM shifts and some of us are not. My only complain is the way it shifts on an uphill on ramp. As I merge, it shifts into 4th. I would like it to stay in 3rd just a little longer. :m2:
 

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2003 chevy trailblazer_ls
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The reason, of course, that the PCM does this is because it has been programmed for the highest economy.

And, I'm not interested in debating the subject, but if you compare today's PCM programing with a vehicle from the '80s, you would call today's PCMs "smart". The problem is in the definition of the proper ratio.

The PCM has the ability to learn driving habits (and that, by the way, is what makes it a smart computer); some of us are happy with the way the PCM shifts and some of us are not. My only complain is the way it shifts on an uphill on ramp. As I merge, it shifts into 4th. I would like it to stay in 3rd just a little longer. :m2:
I agree... But, your complaint is precisely why I wrote what I wrote. BTW, a PCM for Less program can change the shift points. :yes:

I've been driving all sorts of vehicles now for close to 40 years, including 1.5 million miles as a pro driver. Smart vehicles only get you just so far before common sense and a specialty tune come into play.
 
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