[DeTomaso] Final Drive Gear Question

John Buckman jb841 at cox.net
Sun Jun 24 17:38:37 EDT 2012


Shaun,

As the gear ratio gets higher, the gear's diameter has to increase.  Anything larger in diameter than the .620 gear would require too much machining of the shift shaft, and would compromise the shift shaft.  

If you used the .620 5th gear and a 3.78 R&P, you would drop 600 rpm at about 70 mph.  This puts your *true* engine speed at 2050 rpm.  Even with a stock cam, you will need to use more throttle (than before the gear change) as the highway begins to ascend (even slightly).  This will also negatively affect gas mileage. 

Use Lloyd's calculator for swapping gears and R&P's.

http://www.rbttrans.com/Gear%20Ratio/page1.php

John 


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