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09-12-2011, 02:31 PM
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#1 |
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Registered User
Join Date: Sep 2011
Location: San Dimas, CA
Posts: 4
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1988 C3500 Gas Mileage
My 19 year old got his first car. It is a 1988 Std Cab C3500. It has a TBI 454 in it with a TH400 and 3.73 gears in the back. The tires are 30 inches tall. The gas mileage is awful. My question is, is it that because of the 3.73 gears in it? The engine must be running OK, because it passed smog. (California).
My 91 2500 454 Suburban got OK gas mileage, but it had an Overdrive auto trans in it and the rear end gears were not that low. If it is a rear end gear issue, what would be a good street gear ratio for this? He does not tow anything. |
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09-12-2011, 10:50 PM
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#2 | |
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"Oh well, it's a driver."
Join Date: Jul 2008
Location: Nashville, TN
Posts: 3,467
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Re: 1988 C3500 Gas Mileage
Welcome to the board! All I know to say is this: He's 19, with a big block, and a non-overdrive tranny. I'd be shocked if his mpg broke into double digits, regardless of rearend ratio.
__________________
- JB - '93 C1500 SHORT/FLEET SILVERADO, 350/4L60E  Quote:
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09-13-2011, 08:35 AM
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#3 | |
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Registered User
Join Date: Feb 2000
Location: Wichita Falls, Texas
Posts: 3,153
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Re: 1988 C3500 Gas Mileage
My '88 crew cab dually is square body, but that shouldn't make a huge amount of difference. It was born with a 454/TH400 and 4.10s. Even after swapping the TH400 for a 5-speed, the truck still doesn't see more than 8mpg.
A higher gear might help some, but the real issue lies under the hood. You just can't expect much mileage from a 454. Quote:
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09-13-2011, 05:01 PM
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#4 | |
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"Oh well, it's a driver."
Join Date: Jul 2008
Location: Nashville, TN
Posts: 3,467
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Re: 1988 C3500 Gas Mileage
Lol, I was talking about the driver
 I remember how I drove when I was 19...it's basically the way I drive now, at 31...
__________________
- JB - '93 C1500 SHORT/FLEET SILVERADO, 350/4L60E Quote:
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09-13-2011, 05:05 PM
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#5 | |
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Registered User
Join Date: Feb 2000
Location: Wichita Falls, Texas
Posts: 3,153
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Re: 1988 C3500 Gas Mileage
Quote:
And at 34, I don't drive much differently than when I was 19 either. My insanity is just more polished and skilled these days. 
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09-16-2011, 04:35 AM
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#6 |
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Registered User
Join Date: Jan 2009
Location: Louisville,Ky
Posts: 5,811
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Re: 1988 C3500 Gas Mileage
Its a 1ton truck its gonna be hard on gas.
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09-16-2011, 11:45 AM
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#7 |
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Registered User
Join Date: Aug 2011
Location: Dallas Burbs, TX
Posts: 34
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Re: 1988 C3500 Gas Mileage
8mpg....every 454 Chevy gets 8mpg. The key word is 8mpg...
__________________
1998 Chevy K1500 4x4 172K 1999 Chevy k2500 Burban 114K http://i264.photobucket.com/albums/i...luKlrK2500.jpg |
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09-16-2011, 03:09 PM
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#8 |
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Registered User
Join Date: Sep 2011
Location: San Dimas, CA
Posts: 4
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Re: 1988 C3500 Gas Mileage
Well then heck. I am going to build him a 10.5 to 1 396/402. I have enough parts laying around to do that. What I will need is Adjustable Electonic Controls for the TBI to compensate for the the smaller CIs. The problem with the 454 is that the stroke is too big for the Connecting Rod length, and the compression is too low. We will see.
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