This is an OEM Torque Damper from Nissan that I bought a few years back, intending to replace mine. I've never seen one on a Maxima diesel that wasn't bad. They are reputed to be "no longer available".
It's located near the injection pump. One end bolts to a bracket on the engine, the other to the front crossmember area.
(click on any image for larger)
(old, broken one on right for comparison)
From Nismoparts.com,
11290-W1701, $56 plus shipping
Nissan FAST lists this part No. for all years of Maximas with the LD28 diesel engine.
I'd like $45 + shipping for this one.