* Low or No Transmission Fluid: This is the first and easiest thing to check. Low fluid can cause a variety of transmission issues, including inability to engage forward gears. Check the fluid level (with the engine running and warmed up) and its condition (color and smell). Dirty, burnt-smelling fluid is a bad sign.
* Transmission Problems: This is the most likely cause. Several internal components could be faulty:
* Broken or worn clutch packs: These are responsible for engaging the forward gears. Damage could prevent them from properly gripping.
* Shifting forks or linkage: These components physically move the clutch packs to engage gears. Bent, broken, or worn parts can prevent forward gear selection.
* Internal valve body issues: The valve body controls fluid pressure to the clutch packs. Problems here can prevent forward gear engagement.
* Low/Failing Torque Converter: This hydraulic coupling is located between the engine and the transmission and allows for smooth starting in forward motion.
* Neutral Safety Switch: While less likely given it works in reverse, a malfunctioning neutral safety switch could be preventing the forward gears from engaging. This switch prevents the car from starting unless in park or neutral. A faulty switch could be sending the wrong signal.
* Wiring/Electrical Issues: A problem in the wiring harness related to the transmission could also prevent the forward gears from being engaged. This is less common but possible.
* Broken/Worn Drive Shaft: It's rare to only have forward motion affected, but an issue with the drive shaft connecting the transmission to the rear axle could prevent forward power transfer.
What to do:
1. Check the transmission fluid: This is the simplest first step. If it's low or dirty, have it topped off (with the correct type of fluid) or replaced.
2. Have it professionally diagnosed: Given the complexity of automatic transmissions, you'll almost certainly need a qualified mechanic to diagnose the exact cause. They have the tools and experience to properly test the transmission and identify the failed components. Describing the problem (reverse works, forward doesn't) will help them focus their diagnosis.
Ignoring the problem could lead to further damage and a more expensive repair later. Get it checked promptly.
