Here's why and what you should do:
* Valve Body Issues: The valve body controls the flow of fluid within the transmission, directing it to the different clutches and bands that engage the gears. A malfunctioning valve body can prevent reverse and first gear from engaging. This might involve a stuck valve, a worn-out valve, or low fluid pressure.
* Mechanical Problems: Internal problems such as worn clutches, bands, or broken internal components could also be the culprit. These are much harder to diagnose and repair.
* Low Transmission Fluid: While less likely to cause *only* reverse and first gear failure, severely low transmission fluid can certainly lead to shifting problems. Check your fluid level immediately. However, low fluid is usually accompanied by other problems, such as slipping gears or harsh shifting.
What you should NOT do:
* Keep driving it: Continuing to drive the vehicle with these issues could cause further damage to the transmission.
What you SHOULD do:
1. Check the transmission fluid level: This is the first and easiest thing to do. If it's low, it needs to be addressed, but it's unlikely to be the only cause of this specific problem.
2. Have it professionally diagnosed: Take your vehicle to a qualified transmission specialist or a reputable mechanic. They have the tools and expertise to properly diagnose the issue, identify the cause, and provide an accurate repair estimate. Attempting to diagnose and repair it yourself is highly discouraged unless you have extensive experience with automatic transmissions.
3. Prepare for a potential rebuild or replacement: Depending on the severity of the problem and the age/condition of the transmission, a complete rebuild or even replacement might be necessary. This can be a significant expense.
In short, don't try to fix it yourself. Get it to a professional. The longer you wait, the more damage you risk and the higher the repair cost will likely be.
