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A MPH Calculator from RPM and Gearing

by Mike "Doc" Cobine - Procrastination Racing
Software Last Updated June 4, 1999 - Page Updated 6/09/03

This calculator requires a JavaScript compatible browser.

This was originally written for the VetteNet Home Page and Email List (http://www.vettenet.org/)

Fill in your values by double clicking on "number". Then click on when finished. You can also now calculate when using different transmission gear ratios, like in first gear or in overdrive. If you do not know this ratio, you can simply put in 1.00 as this is the typical 4th gear ratio of most 4 sp and 5 sp manual transmissions. See the chart below the table for typical ratios.

This chart has been revised with actual ratios now. I made a few mistakes on the first pass and have corrected them now.

RPM you wish to check Rear Axle Gear ratio (i.e., 3.08, 3.55, etc.) Transmission Gear ratio (i.e., 2.54, 1.43, 1.00, etc.) Tire diameter in inches (24.5, 26, 27.5, etc.)

The speed in MPH is miles per hour.

The same tire and RPM will give the following speeds based on the following gear ratio changes.

2.59 2.73 3.08 3.36 3.55 3.70 4.11 4.56

Typical Transmission Ratios

Transmission	1st	2nd	3rd	4th	5th	6th	Rev
Corvette 3sp	2.21	1.32	1.00				2.51
Muncie Wide 4sp pre-'74	2.52	1.88	1.46	1.00			2.59
Muncie Close 4sp pre-'74	2.20	1.64	1.28	1.00			2.27
Borg Warner T-10 Wide 4sp early	2.56	1.91	1.48	1.00			2.64
Borg Warner T-10 Close 4sp early	2.20	1.66	1.31	1.00			2.26
Borg Warner Wide 4sp '74 up	2.64	1.75	1.34	1.00			2.55
Borg Warner Close 4sp '74 up	2.43	1.61	1.23	1.00			2.35
ZF 6 speed (Corvette)	2.64	1.78	1.30	1.00	0.74	0.49
Powerglide	1.82	1.00					1.82 R
Turbo 350	2.52	1.52	1.00				1.94 R
Turbo 400	2.48	1.48	1.00				2.08 R
700R4	3.06	1.63	1.00	.70			2.29 R
200R4	2.74	1.57	1.00	.67			2.29 R
Richmond OverDrive 6 sp	3.27	2.13	1.57	1.23	1.00	0.76

These ratios are from several sources and believed to be accurate. If you find any discrepancy, please email me.

If you are interested, this program and more are on a disk called "PERFORM -- The Performance Calculator". It is available cheap, $5 plus postage. Or you can mail $4 and a diskette with return envelope and postage. PC versions only, no Mac available.

Or you can steal this for free and try to figure out the other programs. For those worried this is a commercial item, don't. At $5, this is cheaper than most "free" shareware programs.

DOWNLOAD FREE for a short time only Download Perform for DOS

A Windows version is almost ready. A Beta version is available for download as a demo.

Download Perform for Windows

Original Java Script by Stegath Coachcraft and modified to accept original CCS Software Programming. Diskette contains software ONLY by CCS Software.

Comments to Doc / order a diskette | Return to VetteNet Home Page | Stegath Coachcraft

The Serious Stuff

In plain, simple language, don't copy any of this. Someone owns it!
Procrastination Racing and Corvette Doctor are trademarks of Mike Cobine.

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Updated 2/28/02

2.59	2.73	3.08	3.36	3.55	3.70	4.11	4.56