speedo gear thread
Thread Starter
Racer
Joined: Feb 2012
Posts: 421
Likes: 27
From: Harrisburg PA
speedo gear thread
I thought (assumed) I had a 3.08 rear in my stock L48 '77.
I have an 8 tooth drive gear (just replaced), and an 18 tooth driven gear, along with a 27.05 tall tire (255/60/15).
That should yield me the correct (or really close) speedo readout; however, the speedo reads 10% fast (i.e. at a readout of 70, I am actually going 63, readout of 60, I am actually going 54, etc)..
Adding two teeth (by general rule of thumb that each tooth is good for 5%), it should slow the readout to the actual speed...
By that math, my rear gear ration is a 3.36. Did these cars come stock with a 3.36?
I have an 8 tooth drive gear (just replaced), and an 18 tooth driven gear, along with a 27.05 tall tire (255/60/15).
That should yield me the correct (or really close) speedo readout; however, the speedo reads 10% fast (i.e. at a readout of 70, I am actually going 63, readout of 60, I am actually going 54, etc)..
Adding two teeth (by general rule of thumb that each tooth is good for 5%), it should slow the readout to the actual speed...
By that math, my rear gear ration is a 3.36. Did these cars come stock with a 3.36?
Melting Slicks
Joined: Oct 2010
Posts: 2,276
Likes: 337
From: "ɹǝpunuʍop", Adelaide, South Australia
i used this calculator when i did my 700r4 swap recently
http://tri-5.chevyrides.com/speedo.php
got my reading within less than 1-2mph
http://tri-5.chevyrides.com/speedo.php
got my reading within less than 1-2mph
