Verify rear axle ratio

rhphotord

rhphotord

Senior Member
Ok bought this rear axle assembly for my car. It's in great condition externally appearing as the owner suggested as a low mileage take out with virtually no rust and light peeling original paint. I was told it was a 3:78 ratio and the numbers stamped are 9/34 which should be correct. Sounds simple enough. However out of curiosity I locked up one axle to prevent it turning and spun the pinion, counting the revolutions compared to the unretained axle rotation. I cannot count more than 2 full pinion revolutions for every axle rotation! Really baffled by this and frankly think I must be getting stupid in my old age or I have got a 2:10 axle What am I not seeing?
 
rhphotord said:
Ok bought this rear axle assembly for my car. It's in great condition externally appearing as the owner suggested as a low mileage take out with virtually no rust and light peeling original paint. I was told it was a 3:78 ratio and the numbers stamped are 9/34 which should be correct. Sounds simple enough. However out of curiosity I locked up one axle to prevent it turning and spun the pinion, counting the revolutions compared to the unretained axle rotation. I cannot count more than 2 full pinion revolutions for every axle rotation! Really baffled by this and frankly think I must be getting stupid in my old age or I have got a 2:10 axle What am I not seeing?
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If you're holding one axle from turning, you have to double your pinion revs to get the reading. The spider gears cause the free axle to run at twice speed.


Terry
 
Easy way to figure out the ratio, Mart. And 11 years ago. Time to put up more of your golden oldies!
 
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