I've got a 1989 Camaro IROC 305 5 speed. When I purchased the car, I went through all the RPO codes to see what all the options are. It's got a Borg Warner 9 bolt, and the RPO code GM3(3.45 axle ratio) listed in the glove box. So, tonight, I decided to break into the axle to take a look and change the axle fluid. I look at the tag attached to the axle and it says "Ratio 3-27" and the part number on it is 10032270. I only read the tag to clean it up after i'd gotten the cover back on the gear, so I couldn't count the teeth to verify which was correct. I know it's a 14 year old car, but looking things over, I don't see how the axle could have been swapped without some signs of a replacement. I guess I'm wondering what the chances are that this is a factory mistake......Any thoughts from anyone?

9 bolts or 10 bolts?

3.27 is a coporate gear ratio.

The 3:27 is a BW 9-bolt ratio and the only answer to your question is pull the cover again. That ratio is for the 350 and was possibly swapped in over the years by a previous owner. The factory does not make that kind of mistake on a major part.

Well, I'll just have to open the cover back up. Since the axle had the original part number for the 3.27, the entire axle would have had to been swapped. I just find it hard to believe that someone would have swapped the entire axle. Who knows....I'll just have to open it back up....

This also could be a dealer thing. I remember my buddy buying his 87 IROC and the hood had a blemish on it. They swapped the hood off of a 305 TPI. So his emission label said it was a 305 instead of a 350.

They used to switch wheels all the time to make a deal also. Somebody could have wanted 3.45 gears for their 350 and it was the only way to get the deal.

Just something else to thing of.

Replacing the entire axle assembly is a very easy swap. Whoever owned the car before may have blew-up the 3:45 and went to the 3:27 as a matter of ease & convience. My opinion.
So open it up and find out what you have.

No wait I have to correct myself. 2.77, 3.27, 3.45 and 3.70 are BW axle ratios. 2.73, 3.08, 3.23 and 3.73 are coporate gears.

The factory usually doesn't make a major mistake like that; although you may have a factory blunder.

Do you have J65 on your SPID sheet? If not, the previous owner might have swapped out the rear end for the disc brakes.

1989 IROC's with a BW 9-bolt all had the J65 rear disc brake option with the 11.655 rotors & alum PBR calipers. So it was not swapped for that reason. So now this owner has a 3:27 rear which still is not a bad ratio to have. It could have been a 10-bolt
2:73

After reading his post again, he states that the car now has a BW 9 bolt. His RPO's state that he should have the 3.45 ratio, which was only available with the BW rear. The only thing I can think of is the original owner probably blew the rear gears and was only able to find 3.27 gears to put back in. He probably also put the tag on their so people would know it's not a 3.45 anymore. I doubt this is a GM mixup.

There are factory BW 9 bolt rears out there that are open diffs with drum brakes. The majority of them are posi/disc units, but not all of them.

Thanks for all the responses. I was just curious of the general opinion of how it may have ended up this way. Regardless I'm gonna count the teeth in the axle, and then figure out how to check my speedo gear on the tranny. It seems that the speedometer has always read a little low...but then again, it's a 14 year old car.