Final answer:
A worn clutch release bearing or a worn mainshaft rear bearing could cause a noise in neutral in a standard transmission.
Step-by-step explanation:
A worn clutch release bearing could cause a noise in neutral in a standard transmission. When the clutch release bearing wears out, it can create a grinding or squealing noise when the clutch pedal is pressed. This noise can also be heard when the transmission is in neutral.
Similarly, a worn mainshaft rear bearing can also cause a noise in neutral. This bearing supports the mainshaft, which is responsible for transmitting power from the engine to the transmission. When this bearing wears out, it can produce a whining or growling noise, even in neutral.
On the other hand, chipped sliding gear teeth or worn or damaged speedometer gears are unlikely to cause a noise in neutral. These issues usually result in specific symptoms such as difficulty shifting gears or inaccurate speedometer readings, rather than a noise in neutral.