When I pulled away from a stop sign, I heard a pop come from the rear end and the truck started shaking. Now when I drive it I have to take off slow and when it starts to shake let off the gas and ease back into it. Thought maybe it was a broken motor mount but they look ok. the u joints are fine also. im thinking it might be the spider gears inside the axle but not sure. What is your recommendation and estimated cost of fixing? Thank you.