Finding out a rear diff's ratio

[Tyler]

How do you tell what the ratio is of a rear diff?

The only markings i can see are 81 Kn7 and 209B

[Justin]

Is it off the car? If so just count how many spins of the prop flange it takes for the driveshaft outputs to do one revolution

[munk]

Take the cover off and it will be written on the largest gear somewhere... Well mine was

[andy-m]

as justin said. if it's off teh car, bit of tippex on the splines & case of the output and teh same on the prop flange and case and start counting.

input shaft will either turn just under 4 times (3.9) just over (4.1) or about 4½ (4.444) for every 1 turn of the output shafts.

if it's still on the car, disconnect the prop, mark the input flange as above, then put a bit of tape on a rear tyre and with both rear wheels off the ground, rotate the input shaft