Postby DanJetta » Tue Sep 03, 2013 12:47 pm
Here's what I know from replacing a couple of VW transmissions in the past (I hope this is helpful, and someone please correct me if I'm wrong):
Transmissions usually have a transmission code that applies to your model and has been designed for your chassis and engine. Often, transmissions with a different code from the same model will fit your car and function but will not operate entirely as intended. For example, a transmission from a VW Golf Diesel might fit into a VW GTI, but the difference in gear ratios will cause a loss in power, increased fuel consumption and awkward shift points.
As far as going with your production date and up, I think that's just a "best practice" guideline rather than a hard and fast requirement. Manufacturers usually don't change a transmission drastically (if at all) during a body style run unless there is a known design defect (which I don't think the Pathfinder trannies had for R51s).
To be sure, it may be worth calling a few Nissan service managers. From my experience, they know about as much as the minimum wage guy who changes your oil at Walmart, which is why I seriously call 3 and take the average of the answers I get.
Good luck!