My RPO codes state both G80 and G92.
What exactly do I have out of curiosity?

(1991 Z28 350TPI--700R4)

 

You have exactly:

Whatever is in there when you take off the cover and look.


The "codes" indicate that the car came with the optional gears (probably 3.23) and a posi. Who knows if that's what's still in it. Only one way to find out. Have you changed the fluid lately? Then you need to. Make a point of identifying the parts while catching up on your overdue routine maintenance.

 

There should be another G-- RPO code, means like what sofa said. What ever the gear is you have, that gear was an option for that year, and it came with a posi.

 

the G80 RPO code is the posi traction option. The G92 RPO code was the performance axle, simply stated better geared rear axle than then average joe G80, (usually 2:73.) The G92 offered an upgrade to 3:23 ratio(10 bolt). Except in your case, your car came with the 5.7 engine which only utilized the 9 bolt 3:27 rear axle with that engine combo. If its still in your car(that rear) you can crawl under there and read the tag on the axle cover, should say 3:27 ratio. The G92 RPO also included 4 wheel disc brakes, engine oil cooler and performance exhaust. Now if your car doesn't have air conditioning it gets even better, adding heavy duty front brakes, Alum driveshaft, special shocks, hi perf fuel pump and gas tank baffle. Also deletes standard fog lamps.