Is there any way of telling what size rear end gears i have and whats the deal with the # of teeth. how can u tell this

 

This will depend on what year your car is and if it is a 12 bolt rearend or a 10 bolt. If you are lucky it is a 12 bolt becouse there will be a tag on one of the bolts that holds the differential cover on. If it is a 10 bolt you can take the cover off and count the teeth( Not Fun) .I would bet that if it is a 10 bolt rearend the gears you have are for gas milage not torque mabe a 3.42 or something close to that. I am not up on the newer cars but the older ones you can take the vin number off your car and take it to a dealer . They can look it up.On the gear sizes. the lower the gear the more torque you have on take off . the higher the gear the more speed you get at topend. for streat and strip alot of guys I know run a 3.73 gear. It has good torque and it doesn,t kill you motor on the highway.