ok so this is the 4 10 bolt i've had to put in this f@#$ing car in the past 2 years. i have no idea what the gears are in it but i think it is the 2.73 out of a 87 iroc auto. i got 205/60/16 on the rear. i'm at 1500 rpms at 55 mph. i tried to find an math equation to figure it out but i couldnt find it. am i right in assuming there are the 2.73's

 

pull the diff cover to know for sure, otherwise you will always not be 100%

or get the stamping code off the passenger side axle tube and call your local parts counter chevy dealer and have them decode it real quick if you know the year make model it is from

good luck

 

i have no clue what it is off i bought it from some dudes back yard. how will i know if i take the rear cover off ?

 

gears are stamped with numbers like 41/11 etc which would be 3.73 for instance. If you keep breaking rear ends on a 305 with a 5 speed you need to drive more conservatively or drop $2500 for a moser 9" like I did.

 

if you chalk mark the pinion yoke and chalk mark the brake drum and turn the drum 10 times around and count how many times the yoke goes around

divide them to get the ratio

such as if the drum goes around 4 times and the pinion went 10 then you have 4.10 ratio

but if its posi then its half that

 

you know what is crazy it is when i shift from 2-3 and as soon as the wheels stop spinning and grab i get a "CLUNK BOING BREAK" and i give a F@%& !i was going to try to run the BW 9 bolt i hear there way stronger than the 10 bolt.