Speedo gear

StarDiero75

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Howdy guys!

So i noticed my speedo is off, even though when i changed the transmission i got the same exact one, ie 1965 3.03 for a 1965 3.03 same casting nunber and revision and all. Im guessing someone swapped the gear out on the tailshaft for some reason.

The speedo says 40, im doing 36
Speedo says 75 im doing 67

Using these ive calculated what im doing when it says 60, and im actually doing 54.

I believe currently i have a 19 tooth gear, so since im roughly 5 off at 60, do i go up by 1 tooth to 20?

Thanks,
Ryan
 
Ryan, yes give the 20 tooth a try.
 
"...3.03..." rear gear
and what sz tire/wheel?
 
We can do a little math with your observations:

40/36 = 111.11%
75/67 = 111.94%

19 X 111.11% = 21.11
19 x 111.94% = 21.27

So I would say you actually need a 21 tooth gear.
 
mustang6":17kl7ghd said:
We can do a little math with your observations:

40/36 = 111.11%
75/67 = 111.94%

19 X 111.11% = 21.11
19 x 111.94% = 21.27

So I would say you actually need a 21 tooth gear.
So just kidding, i have a 16 tooth in the car. I dont know where i pulled 19 from but i just checked and jt is 16. I will use that math though, thanks!
 
I would check that the odometer matches your speedo findings...They are tied together...It may be just the speedo that is off...It has been a long time, but I thought that there is an adjustment for just the speedo.
 
drag-200stang":qcuj14pr said:
I would check that the odometer matches your speedo findings...They are tied together...It may be just the speedo that is off...It has been a long time, but I thought that there is an adjustment for just the speedo.
No the odometer is matching the speedo. My drive to canada was only about 180 miles, and it recorded about 200 miles.

PS, i drove to Canada in the Ranchero doing about 72 (actual mph, it said 80 mph) for 3 hours. Im so proud, and even happier that i proved my mother wrong that it would make it there and back with no issues.
 
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