3.00 or 3.25 gears

Started by junkyardjeff, May 29, 2011, 07:08:42 PM

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junkyardjeff

May 29, 2011, 07:08:42 PM
I have a maverick 8 inch with 2.79 gears in my 55 sunliner and its noisey,I do have another center section with 2.79 gears that came out of my 37 Chevy p/u that are quiet but I am thinking on another gear to get a little more performance but not rev the motor too much on the highway since it will always have a 3 speed automatic. I have 235/75-15 tires on the rear and dont want to go with 3.55s as they might be a little too much with no o/d,I have 3.55s in the 37 but its a six and has a T-5.

Erick

#1
May 30, 2011, 08:56:39 AM
http://www.carnut.org/specs/tires.html

A link showing common tires sizes and their diameter.


GEAR RATIO = RPM * Tire Diameter / MPH * 336


RPM = MPH * Gear Ratio * 336 / Tire Diameter


MPH = RPM * Tire Diameter / Gear Ratio * 336


TIRE DIAMETER = MPH * Gear Ratio * 336 / RPM

I used the equation to find RPM when settup up the car I'm doing now. Mine is setup with a 3 spd manual w/o OD. 3.00 gear with an 8" Maverick. Rear tire size is 255/70/15.  At 65 MPH * 3.00 * 336/28.9 = 2,267 RPM

With your car at 65*2.79*336/23 = 2,649 RPM

Change to 3.00 the RPM changes to 2,848.

Change to 3.55 the RPM changes to 3,371.

Hope this helps somehow.

Topsterguy

#2
May 31, 2011, 09:22:10 PM
I've gone with 3:00's in a few cars ( 32's so light cars)with T-350 trans etc and they're perfect for the hiway. If I remember right I was at about 2600-2700 RPM at cruising speed, about 65.
"If a man is alone in the forest and speaks, and there\'s no woman around, is he still wrong?"

junkyardjeff

#3
May 31, 2011, 10:59:24 PM
My 65 custom 500 has 3.00 gears with a 302 and 3 speed manual trans and I like the way it runs but the 55 has a 351 that has a longer stroke so I doubt it will feel the same,it looks like I will need to hook up a tach on both the 65 and 55 to see how fast the motors are turning and go from there. I probably should wait untill the 55 gets a Y block before changing the gears but the rear end is noisey and would like to step up on the gears some and get rid of the noise at the same time,it originally had 3.30 gears and the 272 did fine so I am leaning towards the 3.25 gears.

Topsterguy

#4
June 01, 2011, 01:47:54 PM
Quote from: "Topsterguy"I've gone with 3:00's in a few cars ( 32's so light cars)with T-350 trans etc and they're perfect for the hiway. If I remember right I was at about 2600-2700 RPM at cruising speed, about 65.

By the way I was running 235 /75 x 15 tires
"If a man is alone in the forest and speaks, and there\'s no woman around, is he still wrong?"

junkyardjeff

#5
June 01, 2011, 05:01:47 PM
I use 235/75-15s on all of my cars.
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