* Low or Incorrect Transmission Fluid: This is the first thing to check. Low fluid can cause a variety of problems, including inability to shift into drive. Incorrect fluid type can also cause issues. Check the fluid level (with the engine running and warmed up) and its condition (color, smell, clarity).
* Faulty or Worn-Out Bands or Clutches: Inside the transmission are various bands and clutches that engage to allow for forward movement. These can wear out, break, or become contaminated with debris, preventing them from engaging properly. This is a common cause of forward gear failure while reverse still works.
* Problems with the Transmission Valve Body: The valve body controls the flow of transmission fluid, directing it to engage the correct clutches and bands. Worn or damaged valves, or internal leaks within the valve body, can prevent forward gears from engaging.
* Broken Shift Linkage: Although less likely if reverse works, a problem with the linkage connecting the shifter to the transmission could prevent the transmission from selecting the correct gear. This is usually more of an all-or-nothing failure, though.
* Broken or Damaged Input Shaft: While less common, damage to the input shaft, which transfers power from the engine to the transmission, could prevent forward gears from working.
* Torque Converter Issues: The torque converter helps transfer power smoothly from the engine. A faulty torque converter can cause various shifting problems, including an inability to move forward.
Troubleshooting Steps (Do these in order, and stop if you find a problem):
1. Check the transmission fluid: This is the easiest and cheapest check.
2. Listen for unusual noises: While the engine is running, listen for any unusual grinding, whining, or banging noises coming from the transmission.
3. Check the shift linkage: Inspect for any visible damage or looseness.
4. Professional Diagnosis: If you've checked the easy things and still have the problem, take your Caprice to a qualified transmission mechanic. They have the tools and expertise to diagnose the problem accurately. A simple visual inspection isn't enough; often they'll need to drop the transmission pan and check the fluid for debris.
It's important to note that repairing a transmission can be expensive. Before investing in a repair, consider the value of your vehicle and whether the cost of repair is justified.
