is this a rear diff Roller?diff protection?

[ped4599]

Its a vibration dampener. Reduces drive line vibe propagation throughout the rest of the vehicle.

They can be found on some tcases as well.

thanks! I guess i dont need to order one then! you saved me some cash!hehe

[07JeepXK]

Some of the XK/WK's come with them stock right fromt the factory. Like Matt said, its a vibration dampener. My friends 05 Grand cherokee has one. I noticed it when we installed his BDS 4 inch lift last year. He has the 3.7 liter QT1 so obviously its not on all the WK/XK's cause my 4.7 liter doesnt have one. This isnt an upgrade by any means or anything thats going to prevent damage to your Jeep while off roading.