Hello all, I have 97 ford explorer awd, and last weekend it started making this awful pinging/grinding noise when going straight and seemed worse when turning, I thought it was the driveshaft and tightened all the bolts that hold it in place and it went away for about 30 miles and came back, I have checked brakes, rotors, bearings and can not figure it out. it has about 150,000 miles on it. I took the driveshaft out for the time being and it went away completely,Any help is appreciated this is getting really aggravating.