So, according to Jack's transmissions (and lots of other Evo X owners like me who have found out the hard way) your Evo X center diff WILL fail. It's not an if situation...it's a when. Here is a great write up by Jacks who have identified all the improvements Mistu did from the 8/9 trans to the X. He also mentions an upgrade Mistu did for the X that was identical to an upgrade Jacks did to 8/9 trannies when he saw them failing (the input shaft in the 8/9 had ball bearing style end bearings which had reliability issues. To fix this, they made their own bearings that were tapered roller. Mitsu included tapered roller bearings in the X) Here is the link to the article...I HIGHLY recommend you taking your trans/acd to them to get it worked on regardless of the condition of your transmission. It's a ticking time bomb folks...