It's hard to say without feeling it for oneself. The R51 Pathfinders do get "unsettled" over bumps in the road, which is typical for many body on frame trucks. If you feel yours is beyond that characteristic, there are a couple of things you can look at or do. For starters, the rear springs in these vehicles are a bit on the weak side. One way to correct it is to replace the shocks with a monotube design, like Bilstein 4600's, and to install Airlift 1000 air bags in the rear coils. One could also replace the rear coil springs with Moog springs, which seem to be better than the factory coils. Check the condition of the front struts and replace, if necessary. Make sure the vehicle's wheel alignment is good and tires set to correct pressure. Check for play in the inner and outer tie rods in the front steering. Make sure the body mount bushings between the frame and the chassis are good and haven't deteriorated.