Re: Rear-end gear ratios

[Don Dulmage <big-d@xxxxxxxxxxxx>]

Why not go for a drive. take the RPM and the MPh and just do the math. I 
would have someone veryiythe speedo witha neewer car. I get My wife to check 
ine with her PT cruiser. I tell her to drive at 50 MPH which she will do 
exactly and then follow and check mine. I correct my speedo error mentaly 
After that read the tach . Do the math for the rear tire rollout. Work that 
back into the fifty MPH which will give you axle rpm per hour . divide that 
by sixty for axel RPM per minute. Divide that into engine RPM and Bingo! 
minus a tu iny bit of torqueconverter slip you will have the number. Since 
gear ratios are only available in steps it is a simple matter then to figure 
out which one you have.
I know it seems like a bigdeal since we mostlyhate math but in fact a matter 
of minutes will do it. Certainly less time than to jack up the car.
Don
ie 28 inch tire rolls 87.92 inches per revolution. or 7.3266 feet
50 MPH is 50 X 5280 which is 264000 feet per hour divided by 60 which is 
4400 feet per minute.
sincethetire rolls 7.3266 feet per revolution and 50MP is 4400 feet per 
minute then 4400/7.3266= 600Axle RPM
if the engine is turning 2500 RPM at 50 then  2500/600= 4.1666666666666666 
gear ratio. Since the nearestpossible gearratio is 4.30 then we know this 
car has 4.30s. It could not be 4.10s because you cannont invent speedonly 
ose a bit to driveline inefficiency.
Now i have only had one coffee today so my math may need correction but the 
idea is right. It is based on the same way we figure Gear ratio and speed 
for racing except just working from the other end.
----- Original Message ----- 
Don
From: "SB" <polecat2@xxxxxxxx>
To: <1962to1965mopars@xxxxxxxxxx>
Sent: Tuesday, February 24, 2009 11:24 PM
Subject: RE: Rear-end gear ratios


> I'm working on an all-original '64 Dodge Polara 500, 383 2 barrel car
> right now.  It has its original 3:23 sure grip.
>
>
> mikelj@xxxxxxx wrote:
> > I am curious what the gear ratio is for the rear-end of my '64 Dodge
> > Polara 500.  I can't find anything about that on the window sticker,
> > build-sheet, tag, etc.  It seems like it is around 3:00, and I am sure
> > they didn't have many choices in the mundane 383 2 bbl. TorqueFlight
> > setup.  Anyone know?
>
>
> ----
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----
Please address private mail -- mail of interest to only one person -- directly to that person.  I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic.  Thanks!

'62 to '65 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html.