What is likely causing a squeal when the clutch pedal is depressed about one inch?

A squeal occurring when the clutch pedal is depressed about one inch is most commonly attributed to a defective or worn release bearing. The release bearing, often referred to as the throw-out bearing, is a critical component in the clutch system that facilitates the disengagement of the engine from the transmission when the clutch pedal is pressed.

When the clutch pedal is depressed, the release bearing engages with the pressure plate of the clutch assembly. If the bearing is worn or damaged, friction and improper alignment can cause it to produce a squealing noise. This noise is often indicative of the bearing struggling against the pressure from the clutch components, leading to a high-pitched sound which is noticeable at the initial stage of pedal depression.

While other issues, such as a worn clutch disc, might lead to different symptoms associated with clutch performance problems, the specific interplay of the release bearing with the clutch mechanism makes it the most likely cause of a squeal detected shortly after pressing the clutch pedal.