Can you figure the final drive ratio with this info........
05-11-2003, 02:31 PM
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Can you figure the final drive ratio with this info........
2nd gear on an automatic, 1500RMP, Speedo says 30 MPH. Trying to figure if the new PCM thinks I'm running the old gears. :cheers:
05-11-2003, 02:40 PM
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Re: Can you figure the final drive ratio with this info........ (Mag Red Monster)
on a C5 A4, try this:
determine your C5 rear axle ratio
75mph in 3rd; divide the RPM by 1000
.
[Modified by Mike Mercury, 2:41 PM 5/11/2003]
determine your C5 rear axle ratio
75mph in 3rd; divide the RPM by 1000
.
[Modified by Mike Mercury, 2:41 PM 5/11/2003]
05-11-2003, 02:43 PM
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Re: Can you figure the final drive ratio with this info........ (Mike Mercury)
if I could go 75 MPH around here I would try this LOL
05-11-2003, 02:49 PM
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Re: Can you figure the final drive ratio with this info........ (Mag Red Monster)
OK......found out that 2nd gear ratio is 1.62:1 :confused: Is that figured at the trans output shaft?? so if the engine is at 3000RPM the trans out put shaft is spinning at 3000x 1.62= 4860 or 3000/1.62=1851???????
05-11-2003, 04:06 PM
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Re: Can you figure the final drive ratio with this info........ (Mag Red Monster)
Ok MRM, use this formula,
.
.
.
Engine RPM
________________________ = Wheel RPM
Rear end ratio x Tranny ratio
.
.
.
.
.
Wheel RPM x Wheel diameter* x 3.14
___________________________________ = Actual speed in MPH
1056
.
.
.
.
For your situation at 2nd = 1.62
rear end = 3.42 (?)
RPM = 1500
Speed = 21.4 mph almost 30% error.
What are you running for gearing?
.
.
.
Engine RPM
________________________ = Wheel RPM
Rear end ratio x Tranny ratio
.
.
.
.
.
Wheel RPM x Wheel diameter* x 3.14
___________________________________ = Actual speed in MPH
1056
.
.
.
.
For your situation at 2nd = 1.62
rear end = 3.42 (?)
RPM = 1500
Speed = 21.4 mph almost 30% error.
What are you running for gearing?
