Gents, the elusive 4:11 is actually a 4:10 found in those 3/4 ton automatics through 72. Check out this website:

http://www.math-prof.com/Auto/Differential.aspx://www.math-prof.com/Auto/Differential.aspx

You can calculate your velocity knowing your wheel diameter, cruising RPM and final gear ratio,(usually 1:1 on an SM 420) It's a great site. Good Luck, Joe


1947 - 3800 dually known as "Deadwrench"
Link to a few photos

In this world there are givers and takers. The takers eat well, the givers sleep well.