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62 Chevy P/U


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I have a 62 Chevy pickup. It (as most may know) is geared extremely low. At 60 mph, I'm taxing the old 235 straight 6. I want to change the gear ratios for highway driving. Do I look to the rear end, or the transmission? Which, if not both sets of gears should be changed? I know absolutely nothing about transmissions, rear ends, gears or any of the such. I don't know the gear ratio right now, or what I want to change it to. I simply know I want to relieve that old motor (and my fuel bill) somewhat. So..... I don't know whether to dig into the pumpkin or the trans. Any help would be greatly appreciated. Thanks in advance.

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Rear end. Your transmission in high gear unless you have an overdrive unit is turning 1:1. To change the engine RPM at highway speed you need to change your rear end gear ratio. Now doing this will actually affect all gears. My '95 Dodge 3500 360cu.in. 6cyl (5.9L Diesel)has a 3.53 ratio (to 1) that means my driveshaft turns 3.53 times to turn the ring gear one full turn in the rearend. In overdrive @ 55mph I'm turning 1500 RPM. Guys with the same truck but with the 4.11 ratio are turning approx. 1800 RPM @ 55 MPH.<P>As for your truck, you will need to know what ratio you have. The best way is to count the teeth on both gears in the rear end then divide the ring gear number (larger) by the pinion gear number (smaller). this number will give you "x" for your ratio. "X":1 Another quick way to get a ballpark idea is make a line on your driveshaft where it goes into the rear end and you can see it with the truck's axle jacked up. take a piece of tape on put on the fender and make a mark on your tire to corespond with it. turn your tire one full turn and watch your driveshaft, counting full turns then when you stop the tire at it's full turn look at how much farther the driveshaft turned past your mark but not completing the turn. 1/4 turn would be .25 1/2=.50 so your ratio is (driveshaft full turns).(the part)to 1.<P>Hope this helps. if you can find a business that fixs rearends or a shop that builds race cars they should be able to help you more.

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ok ok ok wink.gif" border="0 Hal, if you jack the rearend up both tires off the ground. without a posi-traction unit one tire turns forward one turns backwards the same amount. Or roll the car wil work.<P>I believe one tire up would also work. I'll check it. I have to get under my dad's car rolleyes.gif" border="0 tomorrow anyways. I'll let you know what I find out. But think about, what happens when you get one tire stuck in a mud puddle. one tire doesn't turn (non-posi), the tire in the mud does. the driveshaft has to be turning the gears with the same ratio as if the tire had wieght and traction on it.

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Novaman,<P>I assume you mean to roll the vehicle to count drive shaft revolutions rather than jack up one wheel. I think BOTH tires need to be turning the same number of revolutions (like a rolling vehicle) or else your results will be erroneous. I'd have to think about this some more to be sure, but I think if you were to just jack up one wheel, it would turn twice as many revolutions as the ring gear.<P>Correct me if I'm wrong.

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Novaman,<P>As an analogy, think of a wheel on an axle that is being pushed along a flat surface at a speed of 1 MPH. The axle is moving at 1 MPH. The bottom of the wheel at the point of contact with the surface is not moving at all and the top of the wheel is moving at 2 MPH.<P>Now think of the gears inside the differential. For discussion sake lets say it is a 4:1 ratio. The drive shaft is turning 4 RPM, therefore the ring gear is turning 1 RPM. The gear attached to the end of the axle that is not turning will be our flat surface in the example. The spider gear will be our wheel in the example, and the spider will be its axle. The point on the spider gear that is in mesh with the stationary axle is not moving (relative to the stationary axle). The spider, being rigidly attached to the carrier and ring gear, is turning at 1 RPM. Similarly to the top point of the wheel in the example, the point on the spider gear that is in mesh with the axle that is spinning is moving at twice the speed of the spider. Therefore the axle that is spinning is doing so twice as fast as the ring gear.

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