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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Rear Drivelines, Drive Axles and Gearing => Topic started by: Jim_Hensley on January 19, 2016, 07:25:02 AM

Title: Great RPM calculator
Post by: Jim_Hensley on January 19, 2016, 07:25:02 AM
You can adjust all your variables , choose 4 different rear gear ratios , set your transmission gear ratio, tire size , its really neat.

http://vexer.com/automotive-tools/speed-rpm-calculator
Title: Re: Great RPM calculator
Post by: Irish_Alley on January 20, 2016, 04:48:37 PM
i do like it it seams more interactive the others. But the tallest tires are 36" most wont need much bigger than that. But on the plus side, youre not stuck with the gears or ratio they have set on default you can change them
Title: Re: Great RPM calculator
Post by: zieg85 on January 20, 2016, 05:15:09 PM
I use the Autodyne RPM calculator but it only works with Windows XP and is on my old laptop.  It lists the tire sizes up to 335, aspect 35-80 rims 13-18".  You can compare 2 different transmissions and put any axle ratio and speed and it will tell you the rpm's at that speed
Title: Re: Great RPM calculator
Post by: hatzie on January 20, 2016, 07:17:23 PM
I use the Autodyne RPM calculator but it only works with Windows XP and is on my old laptop.  It lists the tire sizes up to 335, aspect 35-80 rims 13-18".  You can compare 2 different transmissions and put any axle ratio and speed and it will tell you the rpm's at that speed

I never found one that had all the functions I wanted in one place...  so
I made a spreadsheet years ago that calculates rpm tables based on tire size or actual diameter, axle ratios, and transmission gear ratios.  It also factors in transfer case, range box, or overdrive unit ratios into the RPM tables. 
I setup a table at the bottom that calculates speedometer gears and ratio adapters too if needed.
The archive contains two spreadsheets
*-an .XLS file for Microsoft Excel 1997/2000 or newer.
*-an .ODS file for the free Open Office/Libre Office suites calc applet.

 http://www.mediafire.com/download/zk4j8ymtctekx5r/RPM_Gear_Axle_Transmission_TransferCase.zip (http://www.mediafire.com/download/zk4j8ymtctekx5r/RPM_Gear_Axle_Transmission_TransferCase.zip)
(http://johnnynightstick.s3.amazonaws.com/IMAGES/RPM_Table_Spreadsheet.jpg)

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Title: Re: Great RPM calculator
Post by: Irish_Alley on January 20, 2016, 07:27:34 PM
updated my sticky with this new info from hatzie

http://forum.73-87chevytrucks.com/smforum/index.php?topic=30546.msg274738#msg274738