95 nissan pathfinder

i have two questions 1 queston, i have a 1995 nissan pathfinder se v6 4x4, when i start the car, and drive off the engine ticks, and ticks, how do i get rid or can it not go away, and second question, with the same car, when iam at a stop with the car in drive, there is a loud vibration sound comming from the engine compartment, and sometimes it there and sometimes it not, help

Odometer mileage?
Maintenance history?

140000, it does not burn oil, or leaks it, just did a tranny flush and new tranny filter, new starter, every thing else is maintenance on time with it