Ok I am going to be putting a nine inch rear in my car. I will be picking up the axle housing ans shafts form mosier. I just picked up a complete 9 inch rear from a buddy last night for a 100 bucks. I bought it for the third member(3.50 gear and limited slip). My question is there a major difference in third members? Is there on I should stay away from?

The answer to all your question about the 9 inch. http://www.kevinstang.com/Ninecase.htm

The factory Ford Traction Lock differential has a weak cover on the ring gear side. This cover usually breaks, which destroys everything in the case. The after market traction Lock uses a billet steel cover to strengthen the differential. Also, every Ford TL that I have disassembled had worn out clutches. Inspect it well before using it. If there are any cracks in the cover then don't use it. If you will be putting a lot of power to it then don't use it, even if it is good now.

The Detroit Locker is better for drag racing. Don't use an Auburn in the 9 inch, or any rear end as far as that goes.

I wouldn't recommend a WAR case and the N case although it's considered one of the better factory cases using nodular iron, it uses small side bearings and are vary hard to find. I now have a Moser aluminum bolt through case but until now, I was using the very common C7AW-E cases.

The only issue you may have is axle splines. What spline count did you order the axles in? The most common is 28 spline but Ford also offered factory diffs with 31 spline axles. If you ordered 31 spline axles and the third member you picked up is for 28 spline, it won't work. Everything will bolt up but the axles won't go in. Pull an axle from the old housing and count the splines.

To make sure you picked up a 9" and not an 8", see if you can put a socket on the bottom housing nuts. With an 8", all the nuts can be removed with a socket. A 9" needs a wrench for the bottom bolts. Other than that, they'll look the same.