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Gear Ratio

M

Mark1969Bee72

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I’ve purchased a 69 Super Bee a month ago. No broadcast sheet and fender tag is rusted out and in an envelope. Supposedly has 3.23 gears but since it’s at 4000rpm at 50mph, I’m going to guess it’s not. Anyone have an idea what gear might be in this? I’m guessing 4.10.
 
3.73 w 26.5 inch tires w Gearvendor o/d is 3k at 70.
 
Since 4000 at 50mph in high gear calculates to a 6.40 gear, SOMETHING is clearly off. 2nd gear in a 727? Third in a fourspeed? Totally trashed 727? Something.
(4.10 gears in my runner, 3700 got me 65 mph or more. Don't remember exactly.) Had a friend with 283 Chevy with 5.13s, that wasn't that bad.
 
Does it SOUND like 4000 rpm? I would guess the tach is garbage otherwise. O r it could be the speedo.
 
Last edited:
If your going by what speedo is reading in mph it's way off. A GPS app on your cell phone would help? If your like me my only for emergencies no fancy stuff. Any radar signs that tells your speed in your area?
 
You shoulda set up a poll for this one lol. Best bet is Jack it up and figure it out for sure.
 
prodart440 said:
4 speed with the 3/4 linkage on wrong?
Click to expand...
Or, overdrive 4speed with the shift arms on wrong.
No offense meant, but if youre used to late model stuff with an overdrive or two, 3000 rpm can sound like a lot more than it is.
Put a tach/dwell meter on it, and see what it really is.
 
Last edited:
Jack ur car up n spin the tires and see how many times the the driveshaft spins. Surely u can figure it out from there
 
FWIW, 25½ tire diameter, 3.56 R&P gears manual transmission = 3500 RPMs at 72 MPH.
AND
I have to brag a bit, because it's so great: 4.10 R&P same tires, Passon 855 5 speed = 2,750 in .60 5th gear.
Your R&P gears are either 4.56 or one of your gauges (or both) are WAY off.
 
mikeyfrano said:
Jack ur car up n spin the tires and see how many times the the driveshaft spins. Surely u can figure it out from there
Click to expand...


FewRegalJanenschia-size_restricted.gif
 
Have you looked if there is a gear ratio tag on one the housing bolts?
If not, use this formula:
RPM= (MPH x gear ratio x 336)/ rear tire diameter
Just go for a drive at 60mph for example. Note your rpm at that speed. Experiment with different gear ratios until the equation matches your rpm.
 
His claimed 4000 at 50 mph calculates to a 6.40 gear. I kinda doubt it has a 6.40 gear......
Jack it up, find out what gear it has, then find out what is wrong with the speedo, the tach, or the trans.
 
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