Determining rear end gear ratio
10-26-2006, 12:30 AM
#21
richbopp- don't get discouraged. This is all in the interest of science. And remember, when calculating, pie are squared, cake are round. I know this is bass ackwards. That's o.k. My nose runs and my feet smell.
10-27-2006, 02:33 PM
#23
Melting Slicks
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Never got under to see the tag on the rear end. I'm limited here in my shop to a hydraulic floor jack. It's not that easy to crawl under, but I'm determined.
For other questions: tire diameter is 27 inches. P215/75 R15's
At 60 MPH I'm turning 2800 rpm. So from the calculations I was given
(rpm x tire dia) / (mph x 336) = ratio
(2800 x 27) / (60 x 336) = 3.75
and the other calc is revs @ 60/760 would be 2800/760 = 3.68
Both of these are based upon the tach reading 2800. That could be the reason I'm getting different answers. My tach seems to be a little unstable at 60 MPH, as in it bounces just the littlest bit.
For other questions: tire diameter is 27 inches. P215/75 R15's
At 60 MPH I'm turning 2800 rpm. So from the calculations I was given
(rpm x tire dia) / (mph x 336) = ratio
(2800 x 27) / (60 x 336) = 3.75
and the other calc is revs @ 60/760 would be 2800/760 = 3.68
Both of these are based upon the tach reading 2800. That could be the reason I'm getting different answers. My tach seems to be a little unstable at 60 MPH, as in it bounces just the littlest bit.
Last edited by richbopp; 10-27-2006 at 04:01 PM.
10-27-2006, 03:50 PM
#24
Melting Slicks
soundslike 3.70's but be sure that indicated 60 mph is actually 60. The speedo gear in the trans may not be right. In fact that is what will establish the relationship between the speedometer reading and the tach, not the rear end!
09-13-2015, 09:42 PM
#25
Racer
Can someone tell me if a 355 gear was standard for 1966 or was it a 336? I have been told both! Also, was a Posi an option? I have been told that all were posi.
