C4 auto overdrive gear ratio

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Feb 3, 2002 | 04:50 PM

Crusher

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St. Jude Donor '04-'05-'08-'09-'10-'13-'14

C4 auto overdrive gear ratio///rear gear/rpm formula

What is the gear ratio for a 1993 A4 overdrive gear. I think it is .67 but am not sure.

[Modified by Crusher137, 6:04 PM 2/3/2002]

Feb 3, 2002 | 05:02 PM

CFI-EFI

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Re: C4 auto overdrive gear ratio (Crusher137)

Close. 30 % overdrive. The gear ratio is .70:1

Feb 3, 2002 | 05:02 PM

GlockLT4

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Re: C4 auto overdrive gear ratio (CFI-EFI)

yep i agree, i believe it is .7

Feb 3, 2002 | 05:03 PM

FSTRNU

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Re: C4 auto overdrive gear ratio (CFI-EFI)

overdrive is .70 to 1

Feb 3, 2002 | 05:20 PM

Crusher

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Re: C4 auto overdrive gear ratio (93Zeus)

Thanks, I have the formula from DTS to figure out your RPM's with certain rear gears and needed the trans overdrive ratio to do it. Want to move up from the 3:07 but don't want to tach crazy numbers in overdrive at cruising speeds.

Crusher

Feb 3, 2002 | 05:27 PM

Crusher

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Re: C4 auto overdrive gear ratio (Crusher137)

In case anyone wanted the formula...

Q. How can I determine what ratio to use for my application?
A. mph x gear ratio x trans ratio x 336 ÷ Tire Diameter = RPM
Tire Diameter

Example:
70 mph x 3.73 (gear ratio) x .70 (trans ratio) x 336 ÷ 27(tire diameter) = 2274RPM

70 mph with a 3.73 ring and pinion over drive transmission in 4th gear with a 27" tire will perform at 2274 RPM...

[Modified by Crusher137, 4:29 PM 2/3/2002]

[Modified by Crusher137, 6:07 PM 2/3/2002]