troublemaker3

im new here so im gonna explain myself, i just bought a 3rd gen. while in colorado and had my dad drive it back here to buffalo new york. ( no rust was hard to pass up ). its a sr5 auto tranny with a locking diff. 158 k and i paid 8 grand. i knew to check for axle seal leaks and im assuming the timing belt has been replaced with the mileage. while driving at moderate speed there is a wierd rubbing/grinding noise that comes from the underneath. i checked the axle seal and realized the right rear is blown. so i put about 2 quarts of gear oil in untill it started coming out the fill hole and put the cap back on. the noise is still there and when shift from park or reverse to drive it kind of torques the the whole truck forward, is this normal ? i dont think the noise is coming from the diff. and does it sound like my gears are done for?

i know its a long post but i wanted to get all the info out, thanks for any helpfull replies