It could be transmissions mount if the noise is a rattle. Maybe the fluid needs change too; the worn out oil cause slow gear switching and noise too, it says lifetime but it it strongly recommended to change every 80,000 miles. read more
Toyota Camry Automatic Transmissions May Hesitate When Accelerating - 315 reports. Learn about this problem, why it occurs, and how to fix it. Toyota Camry Automatic Transmissions May Hesitate When Accelerating - 315 reports. read more
Due to an apparent known defect in the VTT gear, too much oil drained back into the oil pan which caused un-lubricated VTT gear and related timing chain to make loud metallic clanking noise for a second, upon startup, only, The noise was getting progressively louder and worse. read more