Gear Ratio

[brubakes]

Is it possible to tell what gear ratio I have? The J20 with Dana 60 rear and Dana 44 front came with the 360 and 727 from the factory. Assuming they have not been swapped out what gear ratio should I have.

[The PIG Smith]

The Stock OE ratio for a J20 would be 3:73.

[tgreese]

Confirm by reading the tag under one of the cover bolts, or by reading the tooth count on the ring gear, or by measuring the number of turns of the driveshaft to one complete turn of both of the wheels.

[ABN82MP]

Jack up the rear end and mark the driveshaft with a chalk line. Spin the wheel slowly one turn and count the number of times the driveshaft rotates. 3 1/2 times? Probably a 3.55 ratio. 3 3/4? 3.73. A little more than 4? 4.10. Almost 5? 4.88. Confirm your count by doing it again with the other tire.

Or you could always pull the diff cover and count teeth :D

[tgreese]

Jack up the rear end and mark the driveshaft with a chalk line. Spin the wheel slowly one turn and count the number of times the driveshaft rotates. 3 1/2 times? Probably a 3.55 ratio. 3 3/4? 3.73. A little more than 4? 4.10. Almost 5? 4.88. Confirm your count by doing it again with the other tire.

Or you could always pull the diff cover and count teeth :D
That only works for a locker or posi rear end. Note that both wheels have to complete one turn. If an open differential, you must turn one wheel two turns, or both wheels one turn. You must have one revolution for both wheels. That's the way the differential gears work.

No need to count teeth. The tooth count is stamped into the edge of the ring gear.

[710 Burner]

You could jack up one wheel and put it in N. That would keep the other from spinning.
You could read the tag on the Dana's if it still has it.