I have a 1991 Camaro RS 305 V8 TBI. What size gears do I have in the rear end? I want to put in 3.73 gears, and I'm confused with measurements and stuff (inches diameters stuff like that) Someone help meh!

 

7 1/2 or 7 5/8 ten bolt, gm wanted to confuse everyone by calling it 2 differant things when it's the same. for the ratio pull the cover and count teeth or find it stamped on the ring gear and do the math.

 

Or if you're lucky you can find the stamped data on the right axle tube and decode that for ratio, lockup, and gear sizes. Sometimes they aren't all rusted over so they can still be legible.

 

Like ede said, it's the 7.whatever 10-bolt. If the rear is the original one for the car, and if it still has the original gears in it (neither of which is a sure thing), it's probably either a 2.73 if it's an auto or 3.08 if it's a 5-speed.

In both cases, it's the 2-series carrier, so 3-series gears won't bolt onto it unless you either use the special thick gear set (dumb IMHO) or a spacer. But, since your car is a 91, if the rear is still the original one, it has 28-spline axles, so the $100 posi from SLP will bolt right in. My recommendation would be to get one of those and the gears you want, then it will all just go together right.