jpbgto

iTrader: (4)

I have a 99 z28 and i have heard that they came with 2.73's stock unless you ordered certain packages is this true and how can i find out?

2xLS1

iTrader: (25)

There should be a label on the drivers side door listing all the RPO codes on the car.
Manual cars came with 3.42s - code GU6
Auto Z cars can be either 2.73 code GU2, or 3.23 - code GU5.

jpbgto

iTrader: (4)

thanks for the help

BlackFormula01

Is this the same code for Firebirds?

2xLS1

iTrader: (25)

Same codes. The reason I said Z cars is because all auto SS and WS6 cars will have 3.23s. None of those were ever built with 2.73s. Auto T/As amd Formulas can have either 2.73 or 3.23 gears

Cal

iTrader: (1)

Or if you aren't the original owner and think someone else may have changed the gears, you can take the cover plate off and count the teeth on the ring and pinion. Ring teeth / pinion teeth = gear ratio

Mr Ed

Find an open stretch of deserted road. Then, with your car in 3rd gear (A4), bring the speed up and hold it at 105 mph. If your tac shows roughly 4,700 rpm on stock tires, you have 3.23’s. If it reads 4000 rpm, you have 2.73’s.

Or, if you aren’t a lunatic trying to lose their driver’s license, try 65 mph in 4th. It should be about 2000 rpm with 3.23’s or 1,700 with 2.73’s if my math is correct.

Colonel

Here's my method. Bring the car up to 160 MPH. If you're still in 3rd, you have 2.73s. If you're now in 4th, you have 3.23s.

WARNING: The preceding was ONLY a joke and should only be attempted by trained professionals on a closed course!

Cal

iTrader: (1)

My car tachs 6,200 rpm in 5th gear at 160 mph; yup I have 4.11's!