Q: Tinny sound inside rear of the vehicles engine on the driver side.

Hi there. The sound that you are hearing is a connecting rod bearing that is worn, loose, or damaged. Remove the oil and oil pan to the engine. You can remove the connecting rod bearings one at a time with rotating the crankshaft. Install new connecting rod bearings with white lithium grease. Make sure that you get a builders guide for the torque specs to torque the connecting rod retainers. Then put the oil pan back on with a new pan gasket and put in new engine oil. Start up the engine with the fuel injection or ignition disabled to prevent the engine from actually starting. This will allow the oil to go through the new bearings and prime the oil system. Then hook up the fuel injection or ignition and start the engine. If the sound went away, then you fixed the issue. If the sound is still there, then you may have a connecting rod coming apart from a piston. Then the engine would need to be rebuilt or replaced. If you need further assistance with your engine making a noise, then seek out a professional, such as one from Your Mechanic, to help you.