* Reverse gear problem: The reverse gear teeth or synchronizers within the transmission may be worn, broken, or damaged. This is the most likely scenario given your description.
* Low transmission fluid: Lack of fluid can prevent proper engagement of gears, including reverse. Check your transmission fluid level immediately. Low fluid suggests a leak, which needs attention.
* Transmission fluid condition: Even if the level is adequate, old, dirty, or incorrect transmission fluid can cause problems with gear engagement.
* Broken or misadjusted linkage: The linkage connecting the shifter to the transmission might be broken, bent, or improperly adjusted, preventing the reverse gear from being properly selected. This is less likely given you say it sounds like it's trying to engage, but it's possible.
* Internal transmission problems: More serious internal issues like a damaged clutch pack or other internal components within the transmission could be causing the failure. This is more likely if the problem started gradually and worsened.
What to do:
1. Check the transmission fluid: This is the *first* step. Check the level and condition of your transmission fluid. If it's low, you need to find the leak, but adding fluid may temporarily improve things enough to determine if this is the root cause. If it's dirty or burnt-smelling, it needs changing.
2. Listen carefully: When trying to engage reverse, pay close attention to the sounds. A grinding noise suggests stripped gears. A clunk without engagement points to linkage or internal problems.
3. Professional Diagnosis: Unless you are experienced in auto repair, it's highly recommended to take your Bonneville to a qualified mechanic for diagnosis. Transmission issues are complex and require specialized tools and knowledge to repair correctly. Attempting a repair yourself without the proper expertise could lead to more significant damage.
Ignoring the problem will likely lead to further damage to the transmission, making repairs much more expensive. Get it checked soon.
