ok so i have an 87 camaro, and right now the rear end is stock 2.73 gears im assuming, not real sure...i've got a 274 comp cam and eldebrock air gap on the 350 and a 700r4 with 2400 stall and a shift kit...i want to do a 3.73 posi in the back, but today i was told that if my tranny has overdrive then i should do 4.56 gear ratio, is this a good or bad idea, also this car is my daily driver and come summertime i'll be drive it 60 miles/day, right now im getting 14 mpg...also, does anyone know if these are 26 or 28 spline axles in the 87's, its not iroc or z28, i would appreciate any help!

 

don't assume. Remove the cover and start counting.

 

never assume anything.. as for a gear, i would say a 3.73 would be a good starting point.. not too high, not too low.. but like bobdole369 said, check first.. the easiest and cleanest way is to get the code off the axle housing and look it up.. should be on the passenger side tube, facing the front of the car.. you might have to break out a wire brush to clean off the rust..

 

ok, so theres a code on the axle tube, i was also told that there is a code on the ring gear and that 7.5" came w/ 26 spline and 8.5" came w/28 spline, is this also right? the posi i want to buy is 3.73 ratio from an 88 camaro and i knew that sometime thru they changed it up, so where is a way to figure out what these codes mean?