I have a 2001 Pathfinder. Lately, I've noticed that when trying to quickly pass someone on the highway, the car downshifts but does not gain speed like it should. Even if the car drops into third and 3500 RPM, the speed just will not increase at a rate any higher than a snails pace. Even on roads at lower speeds, (30-50 MPH), a rapid downshift to try and gain speed will result in the engine downshifting and the RPMS increasing, however there just isn't an increase in speed nearly as great as there should be. Any ideas?