Counting the drive shaft turns is easier said than done with a closed
driveshaft. (assuming a stock 50)
Regards,
Doug Pewterbaugh
dpewter@msn.com
Denton, TX
49 3104 216 5-window
----- Original Message -----
From: <Passnb4U@aol.com>
To: <MLayton324@aol.com>; <OLETRUCKS@autox.team.net>
Sent: Thursday, February 03, 2000 10:10 AM
Subject: Re: [oletrucks] tires and gear ratio
> In a message dated 2/3/00 6:26:55 AM Pacific Standard Time,
> MLayton324@aol.com writes:
>
> > ok guys thanks for all the input have looked at several formulas and
> > charts i had understood that all 50 3100 series had 4.10 gear ratios
> did
> >
> > any come with 4.56?
> > all calculations show up different than what i thought i had i have
27
> > inch tires and i am turning almost 4000 rpm at 45 mph needless to say
> this
> >
> > has got to be changed
> > also,what was the height of the factory tires on this vehicle? thanks
> >
> > mike layton
> > 50 3100
>
>
> Mike, off the top of my head, if you have 27in tall tires turning
4000rpms
> at 45MPH, I'd guesstimate you have a high 5:1 rear ratio.
>
> I have 29in tall tires on my '59, with the 4.10 original rear, I turned
> 3000 RPM about 55-58MPH, if I recall.
>
> Are you sure your tach is accurate? Is it set on 6cyl? Are you sure of
> the MPH?
>
> Here's what to do for a quick and dirty method...
>
> Raise one tire off the ground and rotate the drive shaft, see how many
> rev's it takes of the driveshaft to make one rev of the tire, then
multiply
> the rev's by two (assuming an "open" rear, or single wheel drive), that
> number will be the rear ratio...i/e...say it takes you just shy of 2.5
> driveshaft rev's to make the tire go one complete rev, multiply the "just
shy
> of 2.5" by 2, and you'll come up with "a little more than just shy of 5.0.
> Now if I recall, the only ratio just shy of 5.0 would be 4.88:1 R&P set.
>
> Let's say you tire rotated a bit more than 2.5 turns, multiply by 2, and
> you'd have a bit over 5.0, again I think this would put you in the 5.13 or
> 5.33 range, depending on gear ratios available.
>
> If you have a posi rear, both tires will need to be off the ground, and
you
> do not multiply by 2, just take the actual number of tire rev's for the
> ratio, assuming the posi is not shot......
>
>
> Good luck,
>
> Mike
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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