1988 GTA 5.7 Liter automatic. It is a Borg Warner disc rear end, and I know that it must either be 3.27 or 2.77. A buddy of mine who is into 4x4 stuff and Jeeps with 4.88's said he had a good method to tell, I'm just curious if his method is accurate? This is what we did, you tell me: marked the tire and another mark lined up with it in the concrete. Then marked the drive shaft and another mark lined up on the axle housing. Then we jacked it up and turned the wheels while it was in neutral. For every Full turn of the tire, the drive shaft turned 3 1/4 times. We figured this must mean 3.27's. Car feels like 2.77's though, is this method accurate?

 

yep, that's fairly accurate, but as you see, it turned 3 1/4 times, it's just not precise.

check under your console lid for an rpo starting with G and then plug it into the rpo decoder on this site. i.e. GT4= 3.73

 

well 3 1/4 turns would be almost dead on for 3.27's right? Also, the RPO stickers ar missing, but I thought the G92 was the RPO for the newer cars' performance ratio. The L69 cars opted for 3.73's but no the L98 cars. Thanks for the info though.

 

Sounds like a 3.27 ratio. Is there a tag on the rear cover listing the ratio?

Miles
www.9bolt.com

 

No tag, no RPO stickers.....I wish though. For sure though, the 2.77 would have turned less than 3 turns on the drive shaft? How accurate is it?

 

You never know for sure. The best way to check is to pull the covers and count the teeth.

 

That method is accurate, since we only can have specific gear ratios(3.27 is the closest--since you have the 9 bolt rear and the only possible ones are 2.77 or 3.27). If you want it to be more accurate, turn it 10 turns and count the driveshaft turns. Then divide by 10.