American Lead

Does anyone know the gear ratio of the rear end in a 1955 oldsmobile
Thanks

scrappie

Make a mark on the rear wheel and turn one complete revolution. As the wheel turns count how many times the drive shaft turns in complete revolutions. For example: If the wheel spins once and the drive shaft goes around say 2 3/4 turns it probably is close to a 2:78. I could be wrong because it has been so long. If I am wrong please let me know.

American Lead

Thanks for the info guys, this helps alot.

88 coupe

Ratio would be about 5.25. You would have to double the number to compensate for turning only one wheel.

If, in the above example, both wheels were turned (in the same direction) one revolution, the DS would have turned 5¼ revs, and so, would show the actual ratio.

One could also turn one wheel twice, to get the actual ratio.

None of this applies, in cases where only one wheel turns while the car is being driven.

Happy to help.

Norm

Oldsguy

I heard it would be more accurate to turn the driveshaft and count the revolutions on one of the wheels (they should both be up in the air). This is because the driveshaft is the source of the power to the wheels anyway so you are applying power and "simulating" the same action of the car in use.

88 coupe

Is it reasonable to assume the author’s statement was not challenged, at that time?

You have a shaft, with a hand crank on each end. Using one crank, you rotate that shaft, exactly ten revs, and then another ten, using then other crank. Which crank gave you the most accurate reading?

Now let’s split the shaft in two, and add a couple of reduction gears, between them. Now we repeat the same tests using the same cranks. Which crank gave the most accurate reading.

Now put a crank on the subject driveshaft and then one, or both, wheels. Which crank would show the most accurate reading.

I would have asked the author to explain his logic.

OK. The author drove his car for exactly ten miles, then got behind and pushed it for the same distance. All the time, keeping count of all driveshaft and wheel revolutions.

Assuming no tire slippage, what difference, in numbers could we expect between the first and last ten miles of the trip?

Did the numbers change because the wheels were turned, instead of the driveshaft, during the second ten miles?

Norm

American Lead

Thanks for all the feedback guys. I have learned how to do it both ways, and tomorrow when I am doing the transmission gasket I am going to find this out. Thanks for all the info on how to do it.