The transmission system is what allows the driver to control the power generated by the engine. This is done by using the gears of a gearbox. In a manual transmission system, a clutch is used to connect the engine and input shaft together. When the engine generates power, it has an output shaft which sends the power to the input shaft. From there, the input shaft transfers this power to the transmission system. Each time you engage the clutch, the engine power goes to the input shaft.
Both the input shaft and output shaft are rotating during this process. The input shaft bearing is what keeps the input shaft rotating. This bearing depends on oil to keep it lubricated and functioning properly. If the oil levels in the transmission are low, then it creates problems for the input shaft bearing. It won’t be able to keep the input shaft in motion any further. Once this happens, plenty of symptoms will present themselves. Some symptoms will be worse than others.
Bad Input Shaft Bearing Symptoms
Aside from a lack of oil causing your input shaft bearing to go bad, it may just be because it is old and worn out. When the symptoms of a faulty input shaft bearing are present, you need to replace the bearing immediately or risk facing worse symptoms soon.
Below are the top 4 symptoms of a bad input shaft bearing.
1) Engine Noise in Neutral
When you set the gear to neutral, do you hear noises coming from the running engine? If so, then you probably have a worn-out input shaft bearing. As the engine speed changes, the noise will have varying tones and pitches to it. A lack of oil in the gears may be causing this too, so you’ll need to check the oil levels to verify the issue.
2) Constant Gear Sounds
A defective input shaft bearing causes the gears to make constant noise. If you put more demands on your engine by stepping on the gas pedal, then your gears make louder noise of a different tone. You’ll know it is the input shaft bearing because the noise won’t stop, no matter if you stop the vehicle or drive. If it were the output shaft bearing, then the noise would stop when the engine is idle.
3) Gear Slippage
When your input shaft bearing is worn out, the gear may slip into another gear when you step on the clutch. A bad bearing causes the input shaft to move too much. As a result, the gear shafts are not aligned properly and cannot be engaged entirely.
When you go to shift gears, you may feel vibrations coming from the shifter. This is a continuation of the noisy symptoms that you experience when the transmission is set to neutral or when you place heavy demands on the engine. The vibrations won’t be as bad as the noises, but it’s still something to recognize as far as symptoms go.
The cost to replace an input shaft bearing may range from $200 to $300. The part itself only costs about $25 to $75, depending on the make and model of your vehicle. But the labor costs will be much more because it’ll take the auto mechanic more time and effort to get to the input shaft bearing. So, you can expect the labor cost to be around $175 to $225. If you can find a cheap auto mechanic, then perhaps you can cut this cost down by 25% or so. But you’ll definitely have to pay added taxes and fees on top of the total price.
The Causes of Input shaft bearing Noise
You’ll know when there is a problem with the input shaft bearing because you will hear strange noises coming from it. Here are the common causes of the noises:
1) No Lubrication
The number one reason for input shaft bearing noise is a lack of lubrication. This can happen after your input shaft bearing is old and has never been replaced before. The bearing gets worn down faster if you drive a lot each day too. So, keep that in mind.
2) Bad Input Shaft Bearing
It is possible that you have a bad input shaft bearing because it was damaged or has deteriorated over the years. You would probably experience the lack of lubrication first unless something happened to cause it to go bad.
Tips to Diagnose
If you have the gear set to neutral while you release the clutch pedal, then don’t be surprised if you hear some noises coming from the input shaft bearing. The noises should go away after your foot is completely off the clutch pedal. This is a sign that you have a bad input shaft bearing.
Check the condition of the clutch linkage as well. There may be some misalignments in the linkage that can be adjusted in order to eliminate the noises.
Otherwise, you’ll likely have to replace your input shaft bearing as soon as you can. Even if the bearing does not have enough lubricant, it is better to replace the bearing entirely just to be safe.