3:73's and MPG.
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 1,034
Likes: 4
From: Dorr MI
3:73's and MPG.
Just bought a 93 to use as a daily driver. Currently feels pretty peppy even with stock 2:54 gears. From the start of looking for a C4 LT1 I planned on putting 3:73's and about a 2000 stall converter in the car. I previously had a LT1 Firebird and those 2 mods made a huge improvement in acceleration. But back then gas was still under $2.00 a gallon.
So my question is for you guys that have made the swap how much did it hurt your MPG? I used to not care too much but with local 93 octane at 3.65 it is a consideration.
A second question I have is how big of an improvement are the 3:07 gears over the 2:54's? I have seen some of these priced pretty reasonably at Corvette parts places.
Thanks for any advice/help.
So my question is for you guys that have made the swap how much did it hurt your MPG? I used to not care too much but with local 93 octane at 3.65 it is a consideration.
A second question I have is how big of an improvement are the 3:07 gears over the 2:54's? I have seen some of these priced pretty reasonably at Corvette parts places.
Thanks for any advice/help.
Burning Brakes
Joined: Feb 2006
Posts: 1,098
Likes: 1
From: Webster Texas
I went from 3.07 to 3.75. My mileage while the car was a modded CFI car, stock internals, using 3.75's, was low 20's hwy. The 383, w/a 2800 stall converter , at a steady 70mph got 17.9 mpg. All hwy miles. Hope that helps.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
With your current 2.59s, drive a couple of tanks without using 4th gear. That will be about the same as 3.73s.
Subtract another 10% from that since you'll be inclined to waste more gas with the higher gears.
Subtract another 10% from that since you'll be inclined to waste more gas with the higher gears.
Drifting
Joined: Aug 2004
Posts: 1,430
Likes: 2
So your saying he drive it in overdrive. Sounds like he has an auto.
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 1,034
Likes: 4
From: Dorr MI
Yeah, I have an auto. I won't be too concerned with a couple of MPG. If it dropped into the 15mpg range I might be concerned. Weather was fine today. took it out on a cruise. At a steady 70 it was just under 2K rpms, showing 22-24 mpg.
Le Mans Master
Joined: Oct 2004
Posts: 7,706
Likes: 485
From: Everett WA
C4 of Year Finalist (appearance mods) 2019
Well I sugest that you look at the the post made a few days ago about what mpg everyone is getting.
The tc is also going to decrease your milage for the same reason the new gears will ..... your foot
My bet is that if you've got an auto like I do unless your daily driving is on the highway you will be seing an average of about 15mpg.
I will tell you this. If you've got a 2.59 just moving up to a 3.07 will feel like you went for a v6 to a v8
The tc is also going to decrease your milage for the same reason the new gears will ..... your foot
My bet is that if you've got an auto like I do unless your daily driving is on the highway you will be seing an average of about 15mpg.
I will tell you this. If you've got a 2.59 just moving up to a 3.07 will feel like you went for a v6 to a v8
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Burning Brakes
Joined: Mar 2008
Posts: 881
Likes: 24
From: Coquitlam BC
I don't mean to hijack this thread but I'm just curious what you had in your '92 originally and what difference the 3.54's made... I've got 3.07's in my '92 right now and I'm considering swapping to 3.54's in order to launch it faster. I'm not so concerned with the top-end speed, I just want more grunt coming off the line.
Burning Brakes
Joined: Apr 2006
Posts: 1,043
Likes: 3
From: Toledo Ohio
I don't mean to hijack this thread but I'm just curious what you had in your '92 originally and what difference the 3.54's made... I've got 3.07's in my '92 right now and I'm considering swapping to 3.54's in order to launch it faster. I'm not so concerned with the top-end speed, I just want more grunt coming off the line.
Burning Brakes
Joined: Apr 2006
Posts: 1,043
Likes: 3
From: Toledo Ohio
Le Mans Master
Joined: Aug 2004
Posts: 5,141
Likes: 7
From: Metairie Louisiana
I have the 3.07 rear and a 2800 stall. I get about 16.1 mpg in the city and 21-23 mpg hwy. A higher stall or gear would be overkill for mine right now. Traction is already an issue. Without a stickier tire a higher stall and gear are useless. You may actually spin more and add time to your ET's. Spinning does not help performance unless you do that drifting stuff. 
Theres a few things you may want to consider. Are you planning on running DR's or slicks? How much do you drive in the street/rain compared to track use?
Theres a few things you may want to consider. Are you planning on running DR's or slicks? How much do you drive in the street/rain compared to track use?
Last edited by rickneworleansla; Mar 20, 2008 at 05:55 PM.
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 1,034
Likes: 4
From: Dorr MI
99% of my driving will be in dry weather. I also will be doing auto-x with it. I've pretty much for now decided that 3.54 would be as high as I would go. But having said that right now even with the 2.59s I can easily spin the tires in first and it will also set off the TC on the 1-2 shift. Yes I will use special tires (Kuhmos) when I auto-x.
Melting Slicks
Joined: Feb 2006
Posts: 2,240
Likes: 0
From: Cleveland OHIO
99% of my driving will be in dry weather. I also will be doing auto-x with it. I've pretty much for now decided that 3.54 would be as high as I would go. But having said that right now even with the 2.59s I can easily spin the tires in first and it will also set off the TC on the 1-2 shift. Yes I will use special tires (Kuhmos) when I auto-x.