overdrive- good or bad for gas mileage?
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Car: 1991 Chevrolet Camaro RS
Engine: lo3 305
overdrive- good or bad for gas mileage?
This is probably a dumb question but I don't really know what's the difference between overdrive and regular drive. I drive a '91 Camaro RS with the lo3 305 with an automatic transmission. I'm not trying to turn this thing into a racecare. It's my daily driver and it's going to remain stock for the most part. For gas mileage, what the best to use driving around town and on the highway?
I apologize if this has been covered before. I tried searching and came up empty.
I apologize if this has been covered before. I tried searching and came up empty.
#2
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Re: overdrive- good or bad for gas mileage?
when goin down highway its best to use overdrive if ur in town u dont want to use overdrive cause it will wear out your tranny from all the shifting back and fourth. will save u lots of gas if u use it going down the highway
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Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Re: overdrive- good or bad for gas mileage?
I disagree here, just put the shifter in OD and GO. In 3rd you are engaging the over-running clutch pack and that increases the engine braking, hurting your gas mileage. Just us OD or Drive, unless the transmission is shifting/hunting excessively. The original "weak" 700r4 in my 1983 G20 Van behind its equally "weak" 305 lasted nearly 200K miles before being replaced when I put a decent engine in front of it. When I pulled it out, it was still operating smoothly and quietly. The clutches/band were definately showing wear though.
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Car: 1989 IROC
Engine: 305TPI
Transmission: 700R4
Axle/Gears: 2:73 posi
Re: overdrive- good or bad for gas mileage?
I like to have my tranny in third around town because the lock up starts hunting around (on and off) at about 40 MPH and I find that very annoying. The only bad thing is I sometimes forget to put it in 4th when I hop on the freeway
Last edited by Arizona IROC; 11-08-2008 at 11:10 AM.
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Re: overdrive- good or bad for gas mileage?
I disagree here, just put the shifter in OD and GO. In 3rd you are engaging the over-running clutch pack and that increases the engine braking, hurting your gas mileage. Just us OD or Drive, unless the transmission is shifting/hunting excessively. The original "weak" 700r4 in my 1983 G20 Van behind its equally "weak" 305 lasted nearly 200K miles before being replaced when I put a decent engine in front of it. When I pulled it out, it was still operating smoothly and quietly. The clutches/band were definately showing wear though.
#7
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Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Re: overdrive- good or bad for gas mileage?
Last edited by Fast355; 11-08-2008 at 11:26 AM.
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#10
Re: overdrive- good or bad for gas mileage?
so i guess some cars have Drive as well as 3rd gear to select from, so on our cars, would using 3rd gear apply engine braking already? also, is TCC lockup applied in OD & 4th gear only, or, when selected OD, would i also have lockup 1st through 3rd gear?
#11
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Car: 1991 Trans Am
Engine: 305tbi to 350 carb'd
Transmission: 700r4
Axle/Gears: Stock
Re: overdrive- good or bad for gas mileage?
lol when i race i through it in first and do it manually shifting at 5,000 rpm then 2 ,3,OD works greatly but hurts the tranny badly that y i only do in races..
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Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Re: overdrive- good or bad for gas mileage?
When I rebuilt my 700r4, I used MANY HD components, especially when it came to the Transgo Shift Kit. It also comes with extra strength release springs that keep the clutches from applying above 5,500 rpm. It shifts smooth and hard, when I run it hard, I shift about 5,800 and it completes the shift by 6K. Its not all that much harder on the trans than a normal 5,500 rpm upshift.
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Car: 1991 Trans Am
Engine: 305tbi to 350 carb'd
Transmission: 700r4
Axle/Gears: Stock
Re: overdrive- good or bad for gas mileage?
mine when it does it by itself shifts at 4200 GAY
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Car: 91 Trans am
Engine: built 360 TBI
Transmission: built 700r4
Axle/Gears: 10bolt/3.23
Re: overdrive- good or bad for gas mileage?
Here are the 88-92 fbody settings that are controlled by EBL, should be the same for the ECM.
TCC-lock enable CTS -- 51.50 C°
TCC-forced lock -- 100 MPH
TCC-LoGr max TPS% coast unlock -- 1.96 TPS
TCC-LoGr MPH ok to lock -- 34 MPH
TCC-LoGr min TPS% coast unlock -- 1.57 TPS
TCC-LoGr MPH to unlock -- 32 MPH
TCC-HiGr max TPS% coast unlock -- 1.57 TPS
TCC-HiGr MPH ok to lock -- 44 MPH
TCC-HiGr min TPS% coast unlock -- 0.87 TPS
TCC-HiGr to unlock -- 40 MPH
TCC-TPS% opening/closing delta -- to many # to write
TCC-relock delays -- to many # to write
TCC-LoGr TPS% to stay unlocked -- to many # to write
TCC-LoGr to unlock -- to many # to write
TCC-HiGr TPS% to stay unlocked -- to many # to write
TCC-HiGr TPS% to unlock -- to many # to write
By driving at a frequently variating speed between 37-41 without load, right trough the 3-4 gear shift point, or any variating speed and load trough any shift point it would probably be better to select the lower closest gear. These are special situations and do not necessarely hapen during city traffic.
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Car: '70 Bronco, '91 Firebird, '03 Chevy
Engine: roller 302, 350 TB, stock 6.0
Transmission: NP435 Granny 4 spd, 700R4, 4L80E
Axle/Gears: 4.56 spool, 2.73 open, 4.10 broken
Re: overdrive- good or bad for gas mileage?
#16
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Car: 1991 Trans Am
Engine: 305tbi to 350 carb'd
Transmission: 700r4
Axle/Gears: Stock
Re: overdrive- good or bad for gas mileage?
i ordered a t.b.i spacer so im not worrying bout it
#17
Re: overdrive- good or bad for gas mileage?
LOL blkfirebird, what gain in numbers are you expecting?
UglyBronco, i'll agree with you, that's about right - and yeah, not even good noise
thomas, thanks a lot for supplying us with these numbers and clearing my up my question
UglyBronco, i'll agree with you, that's about right - and yeah, not even good noise
thomas, thanks a lot for supplying us with these numbers and clearing my up my question
#18
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Car: 1991 Trans Am
Engine: 305tbi to 350 carb'd
Transmission: 700r4
Axle/Gears: Stock
Re: overdrive- good or bad for gas mileage?
well if you have a good exhaust it will be fine so say what you want man doesnt bother me and for gain out of a t.b.i spacer im not expecting anything so like i said say what you want
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Car: 92 RS Camaro
Engine: 305 TBI
Transmission: T5
Axle/Gears: 3.08
Re: overdrive- good or bad for gas mileage?
In my old 83 z28 it has a heaven sent joy with its almighty 14mpg hwy and like 8-10 city. But after replacing the 700r4 three times and swapping in a th350 I was able to drag race with the juice again and didn't have to worry so much about blowing gears out.
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