* Shift linkage: The linkage connecting the shifter to the transmission could be bent, broken, or out of adjustment. This prevents the selector mechanism inside the transmission from fully engaging third gear.
* Transmission internal problem: This is the most likely and potentially expensive issue. Problems inside the transmission itself could include:
* Worn synchronizers: Synchronizers are responsible for matching the speeds of the gears before engagement. Worn synchronizers make it difficult or impossible to shift into certain gears smoothly. Third gear synchronizers are frequently among the first to wear out.
* Broken shift forks: These components physically move the gears within the transmission. A broken or bent shift fork prevents the third gear from engaging.
* Worn or damaged gears: If the gear itself is damaged, it won't engage properly.
* Clutch issues (less likely but possible): While less likely to directly prevent shifting into third, a slipping or failing clutch could cause the engine to rev high without transferring power effectively to the wheels, *making it seem* like the car is stuck in a lower gear. This would typically be accompanied by other symptoms like slippage in other gears or difficulty getting the car to move from a standstill.
* Low transmission fluid: While unlikely to *prevent* shifting completely, very low fluid can lead to poor shifting and transmission damage.
What to do:
1. Check the transmission fluid: Make sure the transmission fluid level is correct and the fluid itself is clean and not burnt (smells burnt). Low fluid is a quick and cheap check.
2. Inspect the shift linkage: Look under the car and visually inspect the linkage for any obvious damage, bends, or looseness. A mechanic will be able to confirm this more thoroughly.
3. Take it to a mechanic: Given the complexity of transmissions, it's best to have a qualified mechanic diagnose the problem. They have the tools and expertise to determine the exact cause and provide the best repair solution. Trying to fix a transmission problem yourself without experience is highly risky and could lead to further damage. The mechanic will likely need to inspect the transmission internally to diagnose the specific issue.
Don't continue driving the car with this problem, as you risk further damaging the transmission. The high RPMs while stuck in second gear are putting excessive stress on the engine and transmission.
