I have a '71 442 with the stock TO code 3.73 and I'm looking to install a 3.42 so I can enjoy the car on the highway a bit more.

I've read that all '71 442s came with the corporate GM axle and not a type "O". Is this true for all axles including the heavy duty G89 "TO"?

Is there a guide on the net somewhere that will help me ID my axle?

 

Your car was built with the 8.5" 10 bolt. You can reuse your existing posi carrier & install 2.73, 3.08, 3.23 or 3.42 gear sets. If you have not already obtained the 3.42 gears you might consider one of the other ratios but first & foremost decide how tall a rear tire you will be running. 3.23 gears are an excellent compromise between performance & cruise RPM.

 

I had 3.23 gears in both my 70 and an 80 and they are a great all around gear if you don't have overdrive.

 

Thank you : )

Maybe the 3.23 is a better gear for me.

The first thing they ask when I call a shop to have this done is which axle I have. Can you help me verify that the G89 is a corporate 10 bolt and not an O type axle?

 

The carriers are the same in 71. The difference is if you have bolt in axles or not. From 67-70 everything was different.