When a transaxle will not shift into one particular gear, what is the MOST LIKELY cause?

When a transaxle will not shift into one particular gear, the most likely cause relates to the clutch disc being installed backwards. In manual transmission systems, the clutch is responsible for disengaging the engine from the transmission, allowing smooth gear changes. If the clutch disc is installed incorrectly, it can prevent the clutch from fully disengaging.

When the clutch does not disengage properly, the synchronization process for engaging gears becomes impaired. This can result in difficulty shifting into a specific gear, as there may be interference between the gear teeth and the spinning input shaft. This misalignment and lack of effective separation between the engine and transaxle lead to the inability to select that particular gear.

In comparison, while low lubricant levels or a damaged shift mechanism could potentially affect shifting ability, they would generally impact more than one gear or lead to grinding when attempting to shift rather than isolating the issue to just one gear. Loose cylinder block bolts could result in overall engine performance issues but would not typically influence the transaxle's ability to shift into a specific gear.