i got a 91 sentra and the problem is when i go on a up hill something underneath my car starts rattling, sounds like tiny rocks inside my exhaust pipe just rattling. Is it the Catalytic Converter? My car is Automatic and I got a problem with the gearing..when I'm driving off from 0-10 mph the car really pulls and makes a TUG sound after the 10 mph its gone. till it goes on first gear again, will this mess up my tranny or engine? it sounds like a small neutral drop, is it the Torque converter that's too strong making this?