I Have A 1993 Nissan Pathfinder It Has Starting Shaking Really Bad When I Reach 50 Mph?

I worked Nissan parts department for 5 years...... We always sold the rear track bar bushings to solve this. It's set up kind of like a 4-link setup, 2 log bars on top and 2 shot on bottom. That is a total of 8 bushings, and they need to be pressed in w/ a hydraulic press.... Or you can buy the complete links but they are much more expensive.... Make sure to have your wheel barrings and tires checked also, they all work together