cool way to tell 3.73 from 4.10's. .

[JungleJoe]

Most of you may already know, but for the noobs(more than me ) you can jack your car up and use stands so it doesnt fall on you and kill you, but put a dot on the bottom of the tire and one on the bottom of the driveshaft...spin the tire 1 complete turn.Count how many times the driveshaft turns and there you go...3 and 3/4 turns, you have 373's 4 turns and a little, you have 410's.
This is if you bought a car with gears already in it...

 

[NIKwoaC]

To add to that, you have to make sure both rear tires spin the same amount. If your Traction Lok is failing or you have an open differential, and if you don't turn both wheels the same amount, the reading will be off.

 

[TenorPlayinGuy]

^^^ Thats why you spin the driveshaft instead of the tire