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1995 Mercedes SL500
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Discussion Starter · #1 ·
I think my 1995 SL500 has a problem. When cruising down the road, my speed at 56 MPH is at 2000 RPM on the tach. Do I have a problem? Thanks for any help!
 

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2000 SL500
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RPM = MPH X Trans ratio X final drive ratio X 336 / Tire Diameter

Assuming a 4 speed auto with 1:1 4th gear and 2.65:1 final drive ratio and stock tire diameter of 25.7 inch

at 56 MPH I calculate 1940 RPM
at 80 MPH I calculate 2772 RPM

As Alien said, sounds about right. There will be some error in the speedo MPH and maybe even some error in the tach RPM.

I found the formula here
Calculating mph/rpm/Gear Ratio/Tire Size | Rare Car Network (rcnmag.com)
 

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Registered
1995 Mercedes SL500
Joined
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5 Posts
Discussion Starter · #5 ·
RPM = MPH X Trans ratio X final drive ratio X 336 / Tire Diameter

Assuming a 4 speed auto with 1:1 4th gear and 2.65:1 final drive ratio and stock tire diameter of 25.7 inch

at 56 MPH I calculate 1940 RPM
at 80 MPH I calculate 2772 RPM

As Alien said, sounds about right. There will be some error in the speedo MPH and maybe even some error in the tach RPM.

I found the formula here
Calculating mph/rpm/Gear Ratio/Tire Size | Rare Car Network (rcnmag.com)
Thank you for the reply!
 
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