* Reverse band/clutch failure: The reverse band is a component inside the transmission that engages reverse gear. If it's worn, broken, or adjusted incorrectly, it won't engage. This is a very common cause of this specific symptom.
* Reverse gear sun shell or planet carrier issue: These are internal components within the transmission. Damage or wear to these parts could prevent reverse from engaging.
* Low transmission fluid: While unlikely to *completely* prevent forward motion, extremely low fluid level can affect clutch operation and might specifically prevent reverse engagement because of the higher load on the reverse mechanism. Check the fluid level *and* condition (it should be bright red and not burnt smelling).
* Shift linkage/cable problem (less likely): Although less common, a problem with the linkage or cable that connects the gear selector to the transmission could prevent reverse from engaging. This is less likely because forward gears still work.
* Valve body problem: The valve body controls fluid flow to the clutches and bands. A malfunctioning valve within the valve body could prevent the reverse clutch from being engaged. This often leads to other shifting issues as well.
* Low/contaminated transmission fluid: As mentioned, low fluid is a problem, but old or contaminated fluid can also cause problems with clutch engagement.
It's crucial to understand: Diagnosing automatic transmission problems requires specialized knowledge and tools. Simply checking the transmission fluid level is a good first step, but determining the exact cause requires a professional mechanic with experience in automatic transmissions. Attempting a DIY repair without the proper expertise could lead to further damage and significantly increase repair costs.
It's best to have a qualified mechanic inspect the transmission to identify the precise problem and recommend the appropriate repair solution. Ignoring the issue could lead to more severe and costly damage to the transmission.
