How to Troubleshoot Manual Transmissions
- 1). Listen for a clunking noise when accelerating or decelerating. This indicates a problem with the transmission mounting bolts. This is especially true if the transmission is having trouble engaging when you let off the clutch. You'll need to have the mounting bolts tighten to your vehicle's transmission's torque specifications.
- 2). Listen for excessive noise (or any noise, for that matter) while you are in gear. Your transmission shouldn't be noisy, unless you are running special straight cut gears made for high horsepower and racing applications. A noisy transmission while you are in gear can indicate a worn constant mesh gear or damaged synchronizers. These components help to provide a smooth engagement for your gears. When they are worn or damaged, you'll hear a variety of unpleasant sounds coming from your transmission that sound like your transmission is chewing on something metallic.
- 3). Check to see if your transmission is leaking lubricant. Red liquid dripping down from under your vehicle is transmission fluid. This isn't good, for any number of reasons. Mainly, it means that you're not going to be able to shift into gears smoothly (or at all). This is also indicative of some sort of seal failure. The most common failures on older vehicles are a leaky rear main seal or a side gear shaft seal. This needs to be serviced by a shop that specializes in transmission repair.
- 4). Check to see if the transmission slips out of gear. This can indicate loose engine-to-transmission mounting bolts. When the transmission-to-engine mounting bolts loosen due to normal driving, it usually means that the bolts were not tightened to their original service manual torque specification. Torque specs ensure that the bolts are not overtightened or undertightened and that the bolts don't come loose.
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