CV Joint or Constant velocity joint is a core part of your drive shaft. It gives flexibility to your car wheels’ range of motion, transmit power efficiently from transmission to your car wheels while making sure that they rotate at a constant speed.
I know, this is quuuuite the technical piece and it may not be your cup of tea.
If you just want to know whether your car has drive shaft problems, you can read about the Top 3 Drive Shaft Problems and How to Identify It Yourself instead.
In this article, we will explore the following topics:
- What is a constant velocity joint?
- What does constant velocity joint do?
- How do they do it?
- How to maintain your CV-joint drive shaft?
- Where can you repair your CV-joint drive shaft?
What is a constant velocity joint (CV Joint)?
Constant velocity joint is the main component that allows drive shaft do what it does. Structurally, the joints are the heads that attaches to the two ends of your drive shaft.
Virtually all drive shafts will have two constant velocity joint.
If you don’t look carefully, these joints can look like identical twins to an untrained eyes! But, they are definitely not the same.
To distinguish them, we refer to them as the (i) outboard / outer constant velocity joint and (ii) inboard / inner constant velocity joint.
Outer constant velocity joint is a fixed joint that connects to the hub assembly on your car wheels. We call it a fixed joint because it is kept in a fixed position and does not move horizontally or vertically.
But, it can still twists. Try drawing a circle with your head. That’s the same range of motion for constant velocity joint.
On the other hand…
The inner constant velocity joint is a sliding joint that connects to the car transmission. We call it a sliding joint because it slides in and out horizontally.
It is the same kind of motion as when you use a plunger to get your toilet bowl unstuck. Interestingly, it is also called a plunge joint because of that.
I’m sure you have guessed it by now. As the name suggests,
The outer constant velocity joint is located at the outer side of the car (near the wheels).
The inner constant velocity joint is located at the inner part of the car (near the engine).
So far so good? I realised that constantly(pun intended!) typing “constant velocity joint” can make it very exhausting to read. To make life easier, let’s refer to it as “CV-joint” from here onwards.
What does a constant velocity joint do?
The CV-joints are the primary components that allow drive shafts to do their job. They work in harmony to:
- Improve the range of motion of your car wheels.
- Transfer rotational power from the transmission to the car wheels efficiently.
- To turn the car wheels at a constant speed regardless of operating angle.
1. Improve the range of motion of your car wheels.
Imagine having a rigid shaft connected to your transmission and wheels. Your wheels will move up and down together with your car suspension.
If you’re going through a pothole, one of two things can happen:
- If the rigid shaft is strong enough, your entire car will shift upward as one object, causing your ride to be very uncomfortable.
- The rigid shafts will break from the weight of your car, disconnecting the wheels from your car and you might just see your car wheels rolling away from you!
We know that outer CV-joint can twists. This gives it that much larger range of motion to work with when going through potholes.
2. Transfer rotational power from the transmission to the car wheels efficiently.
Ball bearings are found within the joints. Due to the round shape, ball bearings have low contact area and therefore minimal friction during motion.
This allows them to roll and transfer the power without losing too much to the heat.
3. To turn the car wheels at a constant speed regardless of operating angle.
The input shaft and output shaft will always rotate at the same speed regardless of the operating angle. This creates a smooth transfer of power from the input shaft to the output shaft without causing any speed fluctuations.
But how exactly do they do that?
To explain that, I need you to first understand that there are many variations and types of CV-Joint out there. Here are some of them:
- Coupling Type
- Thompson Coupling
- Double Cardan
- Tracta Joint
- Sliding Type
- Tripod Joint
- Double-Offset Style
- Cross-Groove Style
- Fixed Cup Type
- Rzeppa Joint
- Ball and groove
Yes, that’s plenty to read about! But for today, we are only going to focus on the most common ones in Malaysia. Generally, we use Rzeppa joint as the outer CV-joint and Tripod Joint as the inner CV-joint.
Rzeppa joint is invented by an engineer in Ford Motor Company by the name of Alfred Hans Rzeppa in 1926 and patented in 1935. Fun Fact! This joint is the first practical CV-joint ever invented.
It is a type of fixed joint that can twist up to 55 degrees in angle but have no horizontal travel.
In a Rzeppa joint, you will find an outer race, ball bearings, a cage and an inner race.
- The journey begins when you switch on your car engine.
- Input shaft spins when your car engine starts.
- An inner ring is attached to the input shaft.
- Ball bearing goes on top of the inner ring.
- A spherical cage fits and holds the ball bearings in.
- An outer race has grooves for the ball bearings to fit in.
- The outer race has an output shaft that connects to your car wheels.
The ball bearings are where the magic happens. They are the intermediate members between the input and output shaft. In layman’s term, the ball bearings are the middle men that moves power from Point A (input shaft) to Point B (output shaft).
Ball bearings need to be in a specific position to do that efficiently. It has to be in a bisecting plane between the input and output shaft. In order to do that, the spherical cage has 6 slots (one for each ball bearing) to hold and guide them in that angle.
This will make sure that the ball bearing are in constant contact with the outer race which gets the power transferred across to your car wheels.
Tripod joint is developed by Michel Orain of Glaenzer Spicer, France and the patent was finally awarded in year 2000.
It is a type of sliding joint that can twist up to 26 degrees in angle and 50mm of axial travel.
In a Tripod joint, you will find a spider (not the creepy-crawly!), three roller bearings, needle bearings and outer housing.
- Outer housing is attached to the car transmission.
- When the car engine is started, the transmission rotates and so does the outer housing.
- This rotational power gets transferred to the input shaft and then to the Rzeppa joint on the other side.
- The roller bearings and needle bearings are fitted in the grooves inside the housing.
- They are responsible for the axial travel to prevent engine rocking from preloading the bearings.
Why do we use Tripod Joint for inner CV-joint? Why not just another Rzeppa joint? Because it is more cost effective while still sufficient for its intended operating condition.
The operating angle rarely exceeds 20 degrees because it’s attached to the car transmission which is rigidly mounted to the center of the car. When your car wheels turn, the outer joint is the one twisting and doing the work. So, using a Rzeppa Joint which has 55 degrees of operating angle would be an overkill.
How to maintain your CV-joint drive shaft?
We recommend checking your car wheels frequently for any sign of grease splashes. It will only take 5 minutes of your time but can save you hundreds of Ringgit Malaysia on your car repair bill. Hard work definitely pays off!
As with all mechanical moving parts, wear and tear can happen over time.
To avoid these problems, the first line of defence for your CV-joint (and your wallet!) are the constant velocity boots.
They are essentially a rubber cover that keeps the lubricating grease in , which reduces metal-to-metal contact and prolong the life of your CV-joint.
Not only that, they also stop moisture and dirt from entering the joint and grinding against the inner components. If you notice a puncture in your drive shaft cover, get it changed immediately to prevent further wear.
Where can you repair your CV-joint drive shaft?
At certain threshold of wear, you will start to notice the following symptoms:
Yes, these are very common symptoms and it can be caused by any other worn car parts.
So, how do you repair your drive shaft or not?
If you’re a DIY person, we have written an article that will walk you through the Top 3 Drive Shaft Problems and How to Diagnose it Yourself!
But if you don’t have the time, you can leave it to the specialist. #ShamelessSelfPromote
You can speak to D S AUTO‘s customer service and schedule an appointment for a free test drive using our Facebook live chat.
As a drive shaft repair specialist, we can help to…
- Let you know if you have a drive shaft problem.
- Check if your drive shaft can still be repaired.
- Repair your drive shaft.
- Install it.
We hope that you find this guide informative and useful. If you would like to know your drive shaft price, feel free to call us at 03-7805 2020.
Until then, drive safe and drive smart!