Toyota Repair: Toyota V6 4 Runner with48K --and deep loud engine pinging sound, city speed, engine noises

Question
My Toyota has this deep repetitive pinging sound--sounds like it's coming from the engine.  Thought it was a loose belt-its worse when going city speed or slow-actually sounds like a muffler with a hole in it but its coming from the front  I just took it to the dealership--they called and said I put too much oil in the car (I have it serviced regularly so I dont believe that-and just checked the oil recently)-besides, it started doing this months ago--but just recently got louder and louder so I took it in.  Do you have any idea what it might be?  I am checking TSBs but cant find anything like this- btw, the dealer wants 5K to fix--but didnt say what the problem was...yet..  any advice would be welcomed.  signed, broke college graduate-just finished last week!

Answer
What year is the 4runner? I would try to get another opinion because the dealer telling you how much it will cost without telling you what the problem is and what they are going to do just doesn't sound right to me, the normal procedure is to have the dealer diagnose the problem and then let you know what the problem may be and give an estimate to either repair or disassemble the engine to make an estimate for needed repairs, in any case engine noises tend to be expensive repairs but I would still have another facility check it to confirm the first diagnosis and go from there.