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Determining rear end gear ratio

Discussion in 'The Hokey Ass Message Board' started by Six-Shooter, Dec 14, 2012.

  1. Six-Shooter
    Joined: Jul 12, 2010
    Posts: 341

    Six-Shooter
    Member
    from Ohio

    I have a GM 10 bolt rear end (non-posi) in my T-bucket. I tried determing the gear ratio by raising both rear wheels off the ground, marking one of the tires and counting how many times the drive shaft turned (marked also) while making one complete turn of the marked tire. The result was about 1 3/4 turns of the drive shaft per one complete turn of the tire. I tried the same thing with just the marked tire off the ground and got the same result. Also, when I turned the marked tire twice the drive shaft made a little more than 3 turns.

    I originally believed the gear ratio was 3.43:1. Without actually counting the teeth of the ring and pinion gears do the results of the above "turn test" confirm that or does it indicate something else? Thanks!
     
  2. yes , i think you did it right....as long as turned one wheel one turn and the other wheel was stopped.
     
  3. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 12,660

    Johnny Gee
    Member
    from Downey, Ca

    1 3/4 turns X 2 = 3 1/2 or 3.50, so your in the ball park.
     
  4. Six, if you don't know the history or the last time the fluid was changed, why not do it now and find out the ratio at the same time. Just a suggestion of course. Fluid is cheap, replace it with some semi-synthetic or full synthetic and have piece of mind. Don't worry about the rear cover gasket, just use a RTV sealant everyone does. Some of the bolts might be through holes so you need to use a little RTV on the threads and under the heads of the bolts. The fluid is cheap insurance, and the gears are probably marked for the tooth count as well. Just divide the larger number by the smaller number and your done, TR
     

  5. Six-Shooter
    Joined: Jul 12, 2010
    Posts: 341

    Six-Shooter
    Member
    from Ohio

    Great suggestion TR! Thanks, I'll do that!!!
     
  6. Glad I could help Six, perhaps get yourself a tub of Mobil-1 or Valvoline Synthetic wheel bearing grease, two seals and tune up the front wheel bearings at the same time :D
     

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