What could cause a loud clunk when a transaxle equipped car accelerates from a stop?

A loud clunk when a transaxle equipped car accelerates from a stop can indeed be caused by chipped input gear teeth. When the vehicle accelerates, if the input gear has damaged or chipped teeth, it can lead to improper engagement with the other gears in the transaxle. This engagement issue can create a loud noise as the gears struggle to mesh correctly, leading to a significant clunking sound when power is applied.

The condition of the gears is critical for smooth operation of the transmission. If teeth are chipped, the structural integrity of the gear is compromised, which can prevent proper gear interaction and result in abrupt, noisy shifts during acceleration. In contrast, excessive main gear backlash typically manifests as a sloppiness in gear engagement rather than a sharp clunking noise during acceleration, as the gears themselves are not damaged but may simply have too much play. Thus, the presence of chipped input gear teeth is a more direct cause of the loud clunk observed during acceleration.