I recently purchased a new 2012 Nissan Pathfinder diesel and I'm experiencing the same problem with the automatic transmission that other owners are complaining about. When travelling up an incline the transmission will not downshift from fourth gear and the engine will begin to shudder. I find myself second-guessing when pulling out to pass another vehicle, especially when towing a van. I wrote to Nissan twice without getting a reply, and when finally I rang them I was advised that they have not had any other complaints and that there is nothing wrong with the vehicle, but I was advised by the dealer's service department that they get complaints all the time and that it is a computer program problem that can't be fixed. I am not satisfied with the response from Nissan and would appreciate your advice as to what other options I have to try and resolve the problem.
The problem relates to the lock-up torque converter. We have had a number of similar complaints, probably more with the Navara than the Pathfinder, but the same nonetheless. We contacted Nissan about it and were told, "the automatic transmission lock-up setting has been set to optimise fuel economy. Once the vehicle hits 60 km/h the driver needs to depress the accelerator further in order to activate a step-down in gear. This setting does not cause the vehicle to stall. In short, activating a step-down in gear on an incline above a speed of 60 km/h simply comes down to certain driving styles."