Friday, December 4, 2009

Check those axles before you find yourself walking . . .

With winter coming it’s a good idea to check your car’s axles and cv joints. If you read the auto magazines, you’re already getting lots of advice about batteries, antifreeze, and wiper blades. But I’ll bet you haven’t heard a peep about axles, till now. Why not, you ask? Axles aren’t cute or sexy, and they aren’t sold by mass merchandisers. Yet they will strand you more completely than anything short of a broken timing belt.

How could such an important part of your car be so badly overlooked? I don’t know. But there you have it. Today, I am going to take you on a journey toward automotive enlightenment.

Have you considered how the power gets from your car’s engine to its wheels? Many of you know there’s a transmission between the engine and wheels, and some know there’s a differential, the thing that allows the wheels to roll at different speeds on corners.

Some of you know the differential as the thing that lets you get stuck, for it’s the differential that lets one wheel sit still on dry pavement while the opposite wheel spins helplessly on ice.

What connects that differential to the wheels? Axles. The axles are shafts with flexible joints on each end, to allow them to bend up and down as the suspension moves and the wheels steer. Those flexible joints are called cv joints, or constant velocity joints.

Each joint is packed in grease and wrapped in a flexible rubber boot. Joints are supposed to last the life of the car, but they seldom do. What happens is this: The rubber boot cracks and splits, which allows the grease to escape and gritty dirt to get in. When gravel gets exchanged for grease, the joint soon fails, and it comes apart. As soon as that happens, passengers in the vehicle experience the thrill of pedestrian conversion.

Pedestrian life isn’t too bad if it happens somewhere like New York’s Fifth Avenue, but it totally sucks at 2AM on a snowy night in Vermont. Unfortunately, that’s when joints tend to fail.

You see, a boot can crack during the summer and nothing much happens. The grease escapes slowly, but nothing really gets in to hurt the innards. However, when winter arrives, everything changes. The grease gets cold, and it gets thrown off more easily. At the same time, the axle is sprayed with wet salty water from winter roads. A joint that would survive months in the summer can come apart in weeks or days in a new England winter.

And there is no warning that this is going on . . . unless you look. So that is what I urge you to do. Here are some photos to guide you.



In this first shot, you can see a complete undamaged axle. The axle is the black shaft extending across the frame from the left. You can see the rubber boot at the axle’s right end. The wheel hub is on the far right, and the tire would be fastened to that. Chances are, you’ll see something similar if you look under your own car.



This is what a broken boot looks like. In fact, you are looking at the very same axle, when it arrived at our shop. My thumb is spreading the split boot to make it more visible. You can see the beginnings of dirt working their way into the axle.



Here’s what the axle looks like removed from the car. Now the damage is obvious.



This is what the joint looks like inside. As you can imagine, it does not thrive on dirt and salt water



And here we are, fixing the thing. Master technician Bob Toti has taken the axle apart and fitted new boots on each end after cleaning the joints and packing them with fresh grease. The whole process takes a few hours, but it’s vital to the car’s health.

Today, the roads are clean and dry. Tomorrow it may snow. Check your axles and cv joints now.

3 comments:

ACDC said...

Thanks John, that's some really good info. I especially enjoyed the term "pedestrian conversion" and am going to add that to my vocabulary if (and I hope, never, when) my 1994 Volvo should happen to not want to go anywhere. In the meantime, I will climb under to see what my axles look like.

Eric said...

John, I have lived most of my life in Western Mass, and have had CV joints replaced on various cars. But this is the first time that someone explained the problem as well as you did. We don't get the abuse here in Florida that the roads in Massachusetts will do to you, but you gave me some thought. The Rover is fine, but I have a 2002 Saturn as my beach car with 102k on it. Time to check the boots. Woof!

Lance Boldt said...

Great information. Most folks don't know much about their drive train. AutoNetTV has a short, informative video on differential service your readers might enjoy.

http://autonettv.com/2009/differential-service-what-you-need-to-know.html