In my 2005 corolla maintenance manual it suggests tightening the driveshaft bolt every couple of oil change intervals. When I asked my mechanic about this, he said that front wheel drive toyotas don't have the drive shaft bolts, and that it was likely for the AWD matrix. Is he correct? I ask is because I'm hearing a strange sound usually in low rpms in both first and second gears when the engine is under load. I'm wondering if it's this bolt, or my cat, or a lose heat shield or something. please help!