how can i tell which gears my car has..its an 89 iroc manual 305 tpi.

 

Take off the cover and look.

Changed the fluid lately? I suspected as much.... so since you just made your New Year's resolution that today is the day you're going to start catching up on the overdue maintenance you should have already done instead of making excuses for not doing it, make a point of looking at the gears to see what they are while you ALREADY have the cover off, so you don't have to make a special trip under the cover to identify the gears. And of course, check to see if it has posi, so we don't have yet another annoying "do I have posi" post to go along with all the "how can I tell what gear I have" posts.

 

Roughly paraphrased into modern English: If it's a 10 bolt the gear ratio will be stamped on the ring gear as teeth count. 41:15 would be 41/15 or 2.73. Only way to be sure is to look as anything could have been swapped in there over time.

 

An '89 IROC 5-speed is extremely simple to tell your gear ratio. If its a single cat car, it'll be a 10-bolt with 3.08 gears and drum brakes. If its a dual cat car, it will be a 9-bolt with 3.45 gears and disc brakes.

 

Insert the phrase "was and may or may not still be" into the above.

 

Is it the same for Firebirds ?
According to my RPO codes (GU4) I have 3.08 gears and the car has a 10 bolt dual cat set up (stock),also RPO code G80 - axle positraction,limited slip .

 

Yup...

Unfortunately, they don't put clear covers on rears underneath that style of sheet metal wrinkles, either.

You still gotta take the cover off and look. All else is just as much a bunch of guessing and uncertainty as it is on a Camaro.

 

It should be the same for Firebirds too. The G92 package for 89-92 f-bodies includes the better rear end ratio, disc brakes, and dual catalytic converters. You should not have factory 3.08 gears and dual cats.