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12-07-2012, 03:40 PM | #1 |
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rear gears
does anyone have an idea what the gear ratio would be in my 75 c-10, 250-6 cyl. 350 turbo. I can't find a tag on it, or a stamp in the housing. maybe I'm not looking in the right place, Anyway, It sounds like the rods are gonna come out at about 60 mph., and the best it will do on mileage is about 11-12 mpg.
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Art 1975 c-10 stepper 1978 single cab dually 1987 crewcab dually 1986 crewcab single wheel 1948 anglia- (the dixie twister super gas) |
12-07-2012, 03:45 PM | #2 |
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Re: rear gears
thats prob normal mileage!...lol......not 100% but I thought the 6cyl's had 3:73's?....find a 700r4 and some 3:42's...what size are your tires?
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12-07-2012, 03:59 PM | #3 |
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Re: rear gears
235/75/15
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Art 1975 c-10 stepper 1978 single cab dually 1987 crewcab dually 1986 crewcab single wheel 1948 anglia- (the dixie twister super gas) |
12-07-2012, 04:13 PM | #4 |
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Re: rear gears
think thats like a 29" tire, so you prob cant go much bigger...
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12-07-2012, 10:45 PM | #5 |
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Re: rear gears
When you say "It sounds like the rods are gonna come out at about 60 mph", I'm assuming you mean it's revving really high? Sounds like it's probably 4.10 gears then.
A lot of us are getting 11-12mpg, but we're running bigger engines. I would think a 6-cylinder would get better than that, and the gears might be the culprit.
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12-08-2012, 09:02 AM | #6 | |
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Re: rear gears
Quote:
http://www.gmheritagecenter.com/gm-h...olet-Truck.pdf Per the powertrain chart on page 28 base axle is a 3.73 with an optional 4.11. Of course, anything could be in there now so the only sure way would be to do the driveshaft/tire trick or to pull the cover and count teeth. K
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12-08-2012, 09:58 AM | #7 |
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Re: rear gears
Thanks for the help guys, I have had people tell me they had the same or close to what mine has, and they put in a 308, or 2 something gears, and mileage improved to around 17-20 mpg. this sounds like they are full of s^%t, or is that possible to gain that much mpg?
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Art 1975 c-10 stepper 1978 single cab dually 1987 crewcab dually 1986 crewcab single wheel 1948 anglia- (the dixie twister super gas) |
12-08-2012, 01:52 PM | #8 | ||
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Re: rear gears
Quote:
Those high gears (308, 273, etc) also are not so friendly to carburetors. Running down the road at too low of an RPM gets them into all kinds of metering issues. Injection handles this better, but it is still sub-par. You really need to be geared to hit your engine's "sweet spot" and your most used speed. That ideal RPM is Dependant on the engine's size compared to the truck, the cam, etc....
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