A few weeks ago my 02's 4.0 dropped three piston skirts and I recently had it replaced with a 4.0 from an 06. Being a 2006 engine I would normally be concerned about the OPDA failure however the engine was nearly brand new and I would be swapping in the OPDA from my 2002 instead.
OPDA in 2002 block
2006's OPDA that was not used
Well... much to my surprise when the OPDA/CPA was pulled from my 02 we found very abnormal wear on it.
Obviously I bought a new one to put in the 2006 block I thought I just might bring this to the attention of other TJ owners and would like to hear if this is how the other OPDA failures looked.