I have a 2001 cobra with 80k miles. As far as I know the fluid has never been changed in the differential. I always changed my gt's regularly. This looks quite a bit more interesting to do. What do most people do to maintain their IRS differential?
I'm in the same boat. When I get the time I'm draing and refilling with Redline fluid. I've been told Redline and Royal Purple is the best. A local speed shop said it's pretty easy to do on the IRS as long as you have the right tools.
I have never done my 99 Cobra but have done my 97 several times when we put the gears and TA Girdle in. Make sure you add friction modifier if you aren't using Royal Purpl9They have it in the fluid already)