What is a Throw Out Bearing? And Why Does it Make Noise? (2023)

Introduction

Ever had a clutch make loud squealing noises? just like with any car part, it could be a few different problems, but the throwout bearing in a clutch is a possible culprit.

Have you ever wondered what happens when a throw out bearing goes bad in a manual transmission? Here we compare a good vs bad throwout bearing and learn where that sound is coming from.

Hope you enjoy!

Content

Hey everybody welcome back if you're anything like me then.

As you grew up you got to work on cars.

You got to see a lot of mechanical things, but surprisingly I've never actually owned a vehicle with a clutch before.

So, although I know, a lot about what their purpose is and what they're supposed to do I'd actually never gotten a chance to take one apart and learn what the components were so I'd heard people talking about things like throw out bearings pressure plates those kind of things but I never really understood how they all connected together until recently when I was helping somebody to take apart one and diagnose one that had a lot of noise to it and so I thought that was a great opportunity to compare one that was broken to one that was whole and see what the difference is so I'm going to focus.

Only on one particular part and in this case it was the part of interaction.

That went bad with this.

Particular trend with this particular clutch system.

There's a lot of different parts of a clutch, and I'm not going to go into all of those here, but just one really critical one, and that piece that I want to talk about is called the throw out, bearing so a throw out bearing one that's perfectly working.

In fact, this one is brand new, a throw out, bearing has an one end that connects to a piece called a pressure plate.

Now this pressure plate has a whole bunch of springs on it and those springs, as the name implies provide pressure.

But when you have a this throw out bearing connecting to the pressure plate as you step on your clutch pedal, a hydraulic arm like a big fork, presses on this, throw out bearing now they're mounted sideways so as it presses on this throw out bearing it pushes with a lot of force.

Now the inside of this is connected to the transmission.

So it's a shaft, that's rotating, so the inside of this throw out, bearing must be rotating while the outside piece stays stationary.

Now, if it was spinning, if that outside piece was spinning, imagine what that would sound like with this metal rubbing across those forks.

That would be a very loud annoying noise.

So instead the outside of this bearing stays steady and as we apply pressure with that hydraulic fork from the pedal it stays steady, the inside of the shaft can still rotate while the force is applied on the outside.

Now with those forks, they do not apply pressure exactly perpendicular to the shaft that or parallel to the shaft.

So if they're not applying force perfectly and you're pressing on the clutch a lot or the clutch is just old and starting to wear out, then that force is slightly pressing to the side as well as pushing directly parallel on the bearing.

So what that ends up with is wear inside the bearing now, if you've ever heard a bearing, that's gone bad.

It starts to develop kind of a grinding noise, because the inside those nice smooth rotating balls inside are no longer smoothly rotating.

So here's an example of what one would sound like when it's going bad.

Compare that sound to the brand new one, no sound at all.

So if you wonder what does a clutch sound like when it's starting to go bad, imagine applying force with a petal on something that's rotating much faster than I can and listen to that sound now.

In this particular case, there was an extra little bit of a symptom and that symptom was when you applied a little bit of force.

There was a really loud noise, but if you pressed even harder, the noise went away.

Well, that seems odd.

You can't just apply more force and make the bearing start working again, but here's what was going on this pressure plate, which off of a truck, is much bigger this pressure plate, as you can see, there is a lot of wear right on the edges of those forks right here in the middle.

So what was happening was, as the pedal was being pressed, not hard, but gently this bearing that was worn out was not free.

Spinning.

The whole thing was spinning around the axle and as it connected with those springs.

It's continued to spin, both the inside and the outside, and that outside spinning was grinding on those forks or on those teeth, creating a really loud noise.

But if you pressed even harder added more force to this bearing all of a sudden, it would start behaving more like a bearing again yeah.

There was some grinding noise, but it was just due to the bearing inside the outside would be pressing hard enough against those springs that the outside would stop, and the inside would still be spinning again like a real clutch is supposed to.

So.

If you pressed harder on the pedal that noise would disappear, it did not mean that the problem was solved, though this bearing was still very bad, so it required a replacement of the bearing and the pressure plate and the entire clutch assembly at the same time as well, but that noise, especially one that shows up and then goes away when you apply more force, is due to that rotation.

When we only apply a little bit of force of the bearing against those spring teeth, it continues spinning and rubbing on those spring teeth, a little bit more force and all of a sudden now the outside stops and the inside can still spin.

Now, there's also some evidence when I said that that fork does not press perpendicular exactly to the pressure plate.

You can actually see that once again on this pressure plate by that wear pattern inside right here, where you can see that shiny metal that indicates the the metal is actually rubbing that is not perfectly round in the center.

Some of those forks on that spring are actually worn off, while on the other side they are not.

That means that that bearing was not being pressed straight onto there now, that's just a fact of physics.

We can't get away from that, but we do know that once that bearing begins rubbing and goes bad and we hear that noise it's time to replace it, so the parts that are rubbing inside the transmit or inside that clutch.

This is a good candidate of what you might diagnose when you hear that noise is that throw out bearing that noise that comes from the bearing itself, as well as that noise that comes from a stuck bearing rubbing on the metal of the pressure plate that causes that noise.

So I hope this one has been a little bit interesting to you a little bit of just a short tidbit.

It's not all about how clutches work and all about what they do, but I just thought that one was really interesting for me having never seen one before but then getting to see one in action, one that's broken even better and getting to see why it doesn't work.

I always love mechanical assemblies and especially if they're in a vehicle, they're always fun to take a look at so I hope this helps and if you have any suggestions for future things, just drop them in the comments and hope to see you again sometime soon, bye.