Difference between 3:55 and 3:23 gears

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1968dartman

1968dartman

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I am presently running 3:55 gears with 24 in tall tires. At 60 MPH the car is revving at 3100 RPM's. I have a set of 3:23 gears in another pot and was wondering what difference I would see with a gear change. We are looking at a trip next summer and I was wondering if it would be worth my while to change gears ?
 
Not sure if this helps but I just took my Dart out this morning. I was looking at my tach and I noticed at 65 I was turning 2700 RPM. That is with 3.21 gears and 225x70x14 tires.
 
About 300 RPM or so.

It might be easier to go to a 26 inch tire.

Now, if you went to a 3.23 AND a 26" tire it would put you down around 2570.
 
Using a calculator and math ( which hurt my brain) I got about 2800 RPM's. 26 in tires would do the same, but I already have the 3:23 gears.
 
I tried 2:76 gears and HATED them. The car revved too low on the highway and lugged up the hills. I now have three center sections with 2:76 gears sitting in my shop.
 
For what it's worth I swapped in some 3.23 gears when I broke my 3.55's and I checked the fuel mileage after and it gained 2 mpg. I was surprised it was that much with just a 300 rpm drop. Not saying yours will also gain 2 mpg but it sure can't hurt
 
1968dartman said:
I tried 2:76 gears and HATED them. The car revved too low on the highway and lugged up the hills. I now have three center sections with 2:76 gears sitting in my shop.
Click to expand...

Hmm...Sorry to hear that.
After the Spring Fling,I use to get a kick out of getting on the freeway, and flying by geared up big block/hemi cars in my 2.76 geared slant car.
 
I have a 383 Dart GT (1967) and just put a 3.55 SG in it after removing the 2.45 open diff. I haven't replaced the speedo gear yet, so an indicated 90 equals about 63 MPH @ 3,000 RPM and 120 equals 83 MPH. That's with 245/60-14 Cooper Cobra tires. Thinking about taller tires 'cause the 3.55's and small diameter tires (25") have killed my highway gas mileage. 3.23's would prolly have been a better choice, but the 3.55's are great around town. What a difference! I'm thinking about some 15" or 16 inch wheels that would be about 28" tall. I have an 8.25 rear, so changing out the gears ain't as easy as an 8.75.
 
Put a taller tire on it cheap gear change.
 
The math says 9.9%.Adding that same % to the tire circumference, in your case is more logical. A 26.4" tire will do the same, and just happens to be a common 15" tire; the 275/50-15. Or a 245/60-15. Or if you really wanna cruise, the 235/75-15 will get you 28.9", a whopping 20% reduction,or so.

A stock to mild SBM will pull 3.23s no problem-o. Especially with 24s
 
AJ/FormS said:
The math says 9.9%.Adding that same % to the tire circumference, in your case is more logical. A 26.4" tire will do the same, and just happens to be a common 15" tire; the 275/50-15. Or a 245/60-15. Or if you really wanna cruise, the 235/75-15 will get you 28.9", a whopping 20% reduction,or so.
Click to expand...

28.9" diameter tire may cause clearance problems in the front of the 1/4 panel.
 
3.23/3.55 = 91%
You'll be turning 91% of what you are turning now.
3100 x .91 = 2820
No need for charts or crazy formulas here.
 
.32

Not enough to change. See above post.
 
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