I keep seeing this question asked so I thought I would provide a way to answer the question, What rear end and what transmission do I need. Here is the way to figure it out........
Engine rpm X 60 divided by
tire revs per mile X axle ratio X transmision ratio
Equals MPH
2000 X60= 120,000 div by
696.57 X 3.73 X .75 = 61.58MPH with a 700r4 in 4th gear at 2000 rpm
If you want to find out which rear axle ratio you need to run at a given rpm with a 700r4 here is the formula:
Engine rpm X 60 divided by
tire/rev/mile X mph X trans ratio
If you want to run 70mph with a 700r4 at 2000 rpm you need a 3:37 to 1 rear gear
to find out the revs per mile of your tires, take one and mark the bottom of the tire with a piece of chalk. roll it across the floor until the white line comes around. measure this distance convert it to feet and divide 5280 feet to get the rvs per mile . In mycase with a 265/75/15 that was 696.57 revs per mile. Kieth
700R4 final ratio = .75 4 speed, 3 speed = 1.0
If you change tire sizes you can see the outcome on a given ratio, trans, etc.
