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quick question. i think the vetts get like 28mpg pretty much same motor as we have in our truck. i know our trucks weigh more and have 4.10 gears but i dont think that equals to 10-15 mpg less than the vett. Im just wondering why these get that much less mileage. Anyone??
 

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Big gearing difference, big weight difference, huge aerodynamic difference. Easy to figure out if you ask me.
 

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I drove from Jacksonville to Pensacola and back this weekend. One way it is roughly 5 hours.
With the cruise control set on 85, 2 kids, wife and luggage, was getting an average 13.9 to 14.4 on the highway.
We met up with my parents 1/2 way and I drafted him for the rest of the trip (05 yukon denali xl). I reset my average economy thingy and was getting 15.9 to 16.2 going 85.
4:10 not too good on gas but great for passing :thumbsup:
 

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TBSSTony said:
Ding, ding, ding! It's that simple.
Agreed, in order I would have to say (1) gearing, (2) aerodynamics, and to a lesser extent, (3) weight. Once you're going a certain speed, weight doesn't have that much to do with it. I would also add that (4) continually feeding a big 6.0L motor (without DOD) certainly doesn't help.

Gearing, and its main resultant (high RPM at speed) is the big one. Cruising at 2500-2700 RPM just kills mileage. LSx motor efficiency range is ideal at 1800 +/- 100 RPM or so; once you get above 2000 RPM you lose MPG quickly. That's why we really needed the 6L80E. :duh:
 

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TBSS said:
Gearing, and its main resultant (high RPM at speed) is the big one. Cruising at 2500-2700 RPM just kills mileage. LSx motor efficiency range is ideal at 1800 +/- 100 RPM or so; once you get above 2000 RPM you lose MPG quickly. That's why we really needed the 6L80E. :duh:

Yea 2800rpm @ 85 mph
 

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TBSS said:
That's why we really needed the 6L80E. :duh:
Yes, yes we do. Better holeshot and wayyy better mpg too. I'd really like to see someone proficient at doing the 6L80/90E conversions by the time my 3/36 warranty is up.
 

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TBSSTony said:
Yes, yes we do. Better holeshot and wayyy better mpg too. I'd really like to see someone proficient at doing the 6L80/90E conversions by the time my 3/36 warranty is up.
That's right - with a 4.02 first gear you can run 3.23's in the back and have the same off-the-line torque as with our 4L70E/4.10 combo. Mate those 3.23 rears with the 6L80E's .67 final overdrive and you've got 2000 RPM @ 80 mph instead of the 2650 RPM we are running at now. Translation? Another 4 mpg, or more, probably.

That's the main reason I got 2WD....I fully expect someone to have figured out the retrofit within the next 12-24 months, and there's no way you will get a 6L80E to mate up with any transfer case (well, for any reasonable amount of money anyway). :D
 

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you also have to keep in mind the vettes have 6 speed trannys, so they aren't really going up high in the rpm band anyway. i think they should make an 8 speed for us, like in the new ls450 :)
 

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I suppose ANYTHING is possible, but what about a 6spd manual swap? I would guess installing the clutch pedal would be the PITA on this one?
 

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TBSS said:
and there's no way you will get a 6L80E to mate up with any transfer case (well, for any reasonable amount of money anyway). :D
Don't be so sure. I think the Escalade is getting a 6L80E and it's AWD.
 

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:rotfl: :rotfl: I'm guessing that you guys weren't thinking of gass mileage when you signed the dotted line!:D I am making a 7 hour trip this weekend in my 6 cylinder TB. Wanna see if I can pull off 28 mpg. My best so far was 26.9.
 

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TBSSTony said:
Don't be so sure. I think the Escalade is getting a 6L80E and it's AWD.
True, dat. I was thinking present vehicles. It would be great if the 6L80E came out already mated to an AWD transfer case. If so, when would that be? 2008? Sooner?
 

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Pay to Play

I don't care about the mileage. The truck is too darn much fun to complain about mileage. I had a '99 SS and got 31.2 from CT to WI, but I got tired of not being able to drive it in the snow. This is my third TB and I love it. Got out of a 36 month lease 15 months early just to get this SS. If you have to ask...you can't afford it.:):):):):m2:
 

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terdrocket said:
I drove from Jacksonville to Pensacola and back this weekend. One way it is roughly 5 hours.
With the cruise control set on 85, 2 kids, wife and luggage, was getting an average 13.9 to 14.4 on the highway.
We met up with my parents 1/2 way and I drafted him for the rest of the trip (05 yukon denali xl). I reset my average economy thingy and was getting 15.9 to 16.2 going 85.
4:10 not too good on gas but great for passing :thumbsup:

Take that 85 down to 65 and you'd probably get up to 20


But it's all cost effectiveness for you... you want to get there a little faster by spending more money, or spend less and get there a little slower
 

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Weight actually has more to do with it then people think. Vette is light, around 3200lbs so it takes less engine power to get the thing moving. They can afford to put tall gears into the car. An automatic Vette gets around 24mpg. All of this for about 1 sec less 0-60 time. Not bad! If you put 3.23 gears in the SS, it'll be a lot slower thanks to getting 1500 more pounds moving.

In order to get decent peformance out of the SS, they had to go to 4.11 gears. The SS was built for performance first, cruising second.

Aerodynamics takes its toll also. In the USAF we use to call the F-4 a flying brick. One fast brick but it was not aerodynamic and it sucked gas. The F-16 is very aerodynamic and can fly just as fast with only one engine (and about 2/3rds of the weight.

Now if you look at a 0-60 time of 5.5 sec or so for a 4500 pound SUV that can carry 5 in any weather conditions, then the gas mileage isn't that bad.
 

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Dave said:
Now if you look at a 0-60 time of 5.5 sec or so for a 4500 pound SUV that can carry 5 in any weather conditions, then the gas mileage isn't that bad.

Well put... plus if you can afford that type of vehicle, usually paying to put gas in it isn't an issue


Much like if you own an ENZO: if you can afford the car, the $3,000 oil changes are chump change
 

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Dave said:
Weight actually has more to do with it then people think. Vette is light, around 3200lbs so it takes less engine power to get the thing moving. They can afford to put tall gears into the car. An automatic Vette gets around 24mpg. All of this for about 1 sec less 0-60 time. Not bad! If you put 3.23 gears in the SS, it'll be a lot slower thanks to getting 1500 more pounds moving.

In order to get decent peformance out of the SS, they had to go to 4.11 gears. The SS was built for performance first, cruising second.

Aerodynamics takes its toll also. In the USAF we use to call the F-4 a flying brick. One fast brick but it was not aerodynamic and it sucked gas. The F-16 is very aerodynamic and can fly just as fast with only one engine (and about 2/3rds of the weight.

Now if you look at a 0-60 time of 5.5 sec or so for a 4500 pound SUV that can carry 5 in any weather conditions, then the gas mileage isn't that bad.
Agreed about the weight and aerodynamics. Not much you can do about that. The gears, however, leave a lot of room for improvement.

When I mentioned 3.23 gears I was talking about mating them to the 6L80E transmission, which has a 4.02 first gear. Couple that 4.02 first gear with a 3.23 rear, and you get a final drive ratio of approx. 13 in 1st gear.

6L80E + 3.23 gears
4.02 X 3.23 = 12.9846 Final Drive Ratio in 1st gear

This is nearly the same final drive ratio that is presently on our TBSS trucks in first gear:

4L70E + 4.10 gears
3.06 X 4.10 = 12.546 Final Drive Ratio in 1st gear

The 6L80E + 3.23 combo is actually a little better in 1st, meaning you would have more torque with a 6L80E and 3.23's than we presently have with 4.10's and the 4L70E.

:D
 
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