Chock the truck, release the parking brake, put the truck in neutral, jack up the drivers side rear wheels, put matching chalk marks at the driveshaft yoke and housing, also mark the brake drum to the backing plate. Then rotate the wheel and count how many times the drive shaft turns in one revolution of the wheel. Then multiply that number by 2, so if drive shaft turns 3 turns plus about 10% (36*). Multiply 3.10 by 2 = 6.20...the closest rear ratio to 6.20 is the 6.17, so that's what you have...a 6.17 single speed.
Much easier to do than to explain...lol
Mike B
