Nissan didn't just update the tensioner "foot," as it's called, but also the upper timing chains. It appears that the real problem wasn't so much the tensioners but that the chain links were too sharp and cutting into the plastic tensioner "foot." Hopefully, this put an end to the issue. Unfortunately for me, I purchased my 06 with the updated parts already installed by someone else. Apparantly the must have overtightened the primary tensioner bolts because one of them broke, causing the primary chain "slack" guide to fall back against the cover as the tensioner rotated. This caused the primary chain to slack and make a loud rattling noise as it beat against the upper guide and the rear timing cover. It also chewed up the primary tensioner, which is not made of cast iron like older Nissan chain tensioners, but of some type of plastic or resin composite. On the plus side, the chain didn't jump and turn it into a much worse scenario.
As far as the R51's, yes, the 05-07 Pathfinders are the most problem prone. As with any manufacturer, the first two years of any new model tend to have a few 'bugs." You also have to keep in mind 2005 Pathy's were one of the first models built out of the new Canton, MS plant (along with the 05 Quest...and we all know how bad they are!). So, not only did you have new model bugs, but new assembly plant bugs, as well! In 2008, Nissan did a "model refresh" of the R51, so a lot of the problems (albeit not all) were corrected by then. In my experience, the last year of a model run is often the best year to buy! Good time to buy a 2012 Pathy!
