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
|