Anyone go this route? Im running something like 3.73s in the elky. 3000rpm at 60mph. Since this thing is mostly a daily driver, and im driving 25 miles a day. A little more mileage wouldnt hurt. I know its about a 30% reduction but does the mileage go up 30%? I know folks will chime in about a overdrive, but I dont have a overdrive tranny sitting in my yard, BUT I do have a 2.73 10 bolt and a 3.31 12 bolt taking up space. So Id like to use what I have. I could even use the 3.07 gears out of the camaro 12 bolt, but im trying to low buck it. The elky already has 275 60s on back 28" tall. Im getting rid of the 750 eddy and going to a 600 holley. Thanks! jim
3.73s to 2.73s. Mileage gain?
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yes, you will go 30% farther going the same RPMS. MPG wont go up 30%! lol. Your speedo will read 30% slower also
Not gonna help at all if you're driving city traffic all day.
Will benefit on freeway runs tho.
taller gears means more work to get it moving----less work to keep it moving
I have 3:08s in my 79 Chev 1/2 ton LWB
With the 454 and a 4-spd I can coax 14mpg on the hiway under 75mph
moving this thing around town--or dragging the trailer-----lucky to see 7
Will benefit on freeway runs tho.
taller gears means more work to get it moving----less work to keep it moving
I have 3:08s in my 79 Chev 1/2 ton LWB
With the 454 and a 4-spd I can coax 14mpg on the hiway under 75mph
moving this thing around town--or dragging the trailer-----lucky to see 7
G
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·I agree:yes::yes:
I had a SS454 pickup with a 3.73 gear and hunted down a 3.23 for the 14 bolt rear, a complete waste of time. It was a little nicer on the highway but the only time the gas milage improved was when it was sitting in the shop:sad::sad::sad::sad:
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my dad got 16mpg out of his 70 ss chevelle with the 3.31 gears. just didnt open the secondairs on it to much.
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my 70 elky has 2:73 open 12bolt rear, 3 speed auto, gets about 14mpg if keep my foot out of the carb, otherwise it gets about 11 mpg.
Am also running the factory 14 inch wheels.
Am also running the factory 14 inch wheels.
I think that sounds more like 4.10s unless you have a lot of drive-line slippage. (3.73s @60 = appro 2700 RPM, 4.10s @ 60 = approx 3000)
FWIW, I was able to get 16MPG on the highway easily at 70+MPH on a long trip when I had 2.56s and a poorly tuned double pumper, but the accerlation lacked a bit.
The OD trans, eg TKO600, sounds great but for $3k including all the extra do-dads can buy a lot of fuel. I am saving up for one myself but for a summer driver the pay back would be 7 years if I was lucky. I am getting one soley to be able to maintain the rear gearing I want and keep the revs in check. Any fuel benefits would be a fringe benefit.
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I can't help with mileage figures but 2.73 is great for a daily driver you don't intend to seriously race. I happen to have two Chevelle’s with that ratio; a 1969/307ci/TH350/2.73 and 1972/454ci/TH400/2.73; they both love 60-70 mph...:thumbsup:
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doh!! he beat me to it...i was going to see if there was any negotiating about one of those 3.31 sets you have, possibly the whole rear end....it would make your conversion MUCH more affordable.
:yes:
what going to be the deciding factor in your mileage improvement or not ..... is your take off speed .... if you expect the same get up & go :noway: your wasting your time as all the improvements in MPG will be lost at take off , if you start babying it away from the lights then you'll see the improvement from the higher gears ...... BTDT
Keith, it maybe 4.10s in the elcamino. BUT, it is a 10 bolt. not sure if you'd still be interested.
Jake the 3.31's is actually in my spare 12 bolt. We have another elcamino and chevelle with that ratio, so Im keeping it around as a backup.
The 3.07 ratio is the 70 camaro 12 bolt thats suppose to get installed one of these days in my camaro. jim
Jake the 3.31's is actually in my spare 12 bolt. We have another elcamino and chevelle with that ratio, so Im keeping it around as a backup.
The 3.07 ratio is the 70 camaro 12 bolt thats suppose to get installed one of these days in my camaro. jim
Years back I had a 350 in the car with a 700-R4 and 3.31 gears have to look at the old tire size but would consistently knock down 25 mpg on the eway with it on trips. The car loved Power Tours. The motor was slightly built up and still performed rather nice. In this trim the car would run bottom 13's not fast but no slouch. I don't remember city mpg's since at the time fuel was cheap. Now is a different story.
I don't understand why your engine turns 3000 rpm's at 60 mph with a 3.73 and a 28" tall tire to begin with.
My truck turns 1900rpm's at 60 with a 3.42 and a 28" tall tire.And I have a 350 turbo,non lock up converter.With the other "electronic 350 trans" and a lock up converter it spun 1650 at 55mph.Shouldn't,your rpm's should only be 300 higher than mine at 60 mph?
What's up?And sorry if I hijacked your thread,Eric.
My truck turns 1900rpm's at 60 with a 3.42 and a 28" tall tire.And I have a 350 turbo,non lock up converter.With the other "electronic 350 trans" and a lock up converter it spun 1650 at 55mph.Shouldn't,your rpm's should only be 300 higher than mine at 60 mph?
What's up?And sorry if I hijacked your thread,Eric.
2.73's and a Qjet would pull some decent mileage
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I punched the above spec's into an RPM formula and came up with the following numbers...3.73's/28" tire @ 60 mph = 2685 rpm and 3.42's/28" tire @ 60 mph = 2462 rpm's. Both using a transmission high gear ratio of 1 to 1.....
Edit: With 2.73's/28" tire @ 60 mph = 1965 rpm....and 3.31's/28" tire @ 60 mph = 2383 rpm.
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