by morrisg » Sun Oct 23, 2011 8:05 pm
Plan on using a transmission jack to lower the diff when it comes out as it is heavy and can easily crush your head. Besides, you will need one to get it back in the car as you must carefully line up the upper ears of the diff with the bolt holes on the chassis. To make this easier, I used a flashlight and an inspection mirror tilted to view the bolt holes in the chassis through the mounting ears of the diff. When you can see each side line up, then it's easy to start the bolt to hold that side in place.
It isn't hard, but you do have to take most of the rear suspension apart to get the axles to move far enough to come out of the diff. Plan on new C clips to hold the axles in the new diff and new oil seals for both axles. These are cheap parts that might prevent having to take the diff out a second time to replace them if they fail/leak.
Mark your drive shaft across the rear flanges where you will disconnect it so you can line it up in the same place on reassembly.
Get a shop manual and study how to align the transmission (measure distance through the cross brace) so you can get it straight before torquing down the power plant frame bolts on reassembly. This aligns the transmission output with the differential so the driveshaft is very straight and within tolerance. This can help keep reduce any driveshaft vibrations. Again, this isn't hard but you need to check it before disassembly so you can get it put back together correctly.
I put an OS Giken in a spare complete differential into my 09 NC and it was so much better than the stock torsen. However, I autocross my car in STR class which is what made it worth it. I can just plant my foot on the gas on corner exits and there's no drama whatsoever. My friend autocrosses an 06 NC with the stock diff and a year later he's still trying to tune the suspension to keep the rear hooked up on corner exit. He drove mine and is now looking for an OS Giken.
Good luck and I'm sure you will enjoy the Quaife!