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Differential Gear Ratio Determination Without taking anything apart, and without peeking at the speedometer drive gear case, what is your process to physically determine the differential gear ratio?
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Re: Differential Gear Ratio Determination Mark front pulley, mark tire, roll tire one revolution and count the engine revolutions.
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Re: Differential Gear Ratio Determination If you don't want to roll the car forward (don't have space, etc.) you can jack up one wheel in the back, mark the tire, and count how many revolutions of the crankshaft it takes to make that one tire go around fully 2 times (not 1) with the transmission in High gear. Use the hand crank and have someone watch the tire while you crank (it is easier with all of the spark plugs out).
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Re: Differential Gear Ratio Determination RE: Differential Gear Ratio Determination
EASILY find Differential Ratio and Compute engine RPM @ a given speed vs the ratio. Jack up rear end just enough for1 wheel to clear & support with jack stand. Remove top filler plug, wipe oil off one ring gear tooth and mark it with a dab of white paint. Rotate a tire counting the number of ring gear teeth. 34 = 3.78:1 37 = 4.11:1 39 = 4.56:1 Also see http://www.fordgarage.com/pages/rearaxleratios.htm Compute your Engine RPM at a given speed with your axle ratio. Assumes model A is in third gear (1:1 ratio) and not in overdrive if you have one. Engine RPM is egual to: Speed in MPH times Axle Ratio times 336 Divided by the Tire Height. 336 is a constant. Example: 55MPH, axle ratio 3.78, 30 inch tire height gives Engine RPM of 2,328.48 |
Re: Differential Gear Ratio Determination I like that one Terry!
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Re: Differential Gear Ratio Determination I mark crankshaft pulley, on level ground, put in 3rd with valve stem up on tire, roll car forward till valve stem up again while counting revolutions, --- 3-3/4 about= 3:78
4 plus a little = 4:11, 3-1/2 =3:54 , usually I grab front wheel to move car so I can watch pulley, and feel position of valve stem |
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fyi: 3.54 = 11 39 4.56 = 9 41 |
Re: Differential Gear Ratio Determination Quote:
Found it somewhere on on one of the forums. |
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