Our 70 FB is a 302-2v so I am assuming it has an 8 inch.I have done some searches on the web but I cannot find anything definative other than pulling the third member and measuring the ring gear. What is the most definative way to tell if a rear axle is a 9" or 8"? Also, is there any upgrades that can be done to an 8" to handle more torque?

 

If you can get a socket on all of the nuts holding the third member in, it is an 8". On a 9", you have to use wrenches on a couple of them.

 

theres also a large hump on the back of the9"s thats not on the 8"

 

Well, according to the above, we have an 8 inch rear. Oh well....not surprised.

Before we yank it and replace it, is there any upgrades that are worthwhile or should we just go shopping for a 9 inch? We are planning for over 600HP.

 

go for the 9.

 

Better get some 31 spline axles too.

 

Theres a metal tag on the diff with some numbers and letters give me them ill tell what you got.

 

These are the only numbers we can find....they are on the third member.




[IMG]local://upfiles/61121/3FF3C176492347ADB43599BE1E7EFFD7.jpg[/IMG]

 

It is most likely an 8. You can buy an 8 inch that will handle quite a bit of power. It is more than a 9 inch but most people will not have enough power to do any damage. Unless you have some 500 Horse monster under the hood don't worry too much.