Rear Wheel Bearings
By Ron Bramlett

(From our February 2000 Newsletter)

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   If you ask a shop to do this, they should say no! I know it happens because I've had people want me to do it for them.

   A few years ago, when Mustangs Plus was doing customer work, one of our customers needed a rear axle with a good bearing for his ‘65. All he could find was a ‘72 axle, which was too long for his ‘65, with a good bearing. So he bought the ‘72 axle for $35.00 from the local junk yard and took it to a local shop and asked what they would charge to press the bearing off the ‘72 axle and then press it onto his ‘65 axle. They wanted $20.00 to do it and he thought that was too much for the job. So he brought it to us to see if we would charge less. I was shocked that the other shop agreed to do it!

    In the end, it worked out that for about another $15.00, he could buy a new bearing and retainer and have us install it on his axle, which is exactly what he ended up doing.

     OK. No more sermons. You get the idea. Now, on to rear wheel bearings. Ford made two different rear wheel bearings which we can find in our classic Mustangs. Known as small and large bearings, our ‘65 to 73's all came from the factory with the small bearings, even if they came with the 9" rear end. But over the years, many 9" rear end swaps have been made to our classic Mustangs.

    Several of these 9" rear ends have the large bearings. The Lincoln Versailles, Mercury Monarch, and Ford Granada, to name a few. Another popular swap is the ‘57 Ford rear 9" rear ends which came in passenger cars, station wagons and Rancheros. The ‘57 passenger cars have the 9" with the small bearings, the station wagons and Rancheros have the large bearings.

    Remember I said that the rear wheel bearing is the only thing that holds the wheel to the car? That is true. And false. As our classic ‘65 to 73 Mustangs came stock from the factory, it is true because they never came from the factory with rear disc brakes. As they are converted to rear disc brakes, it is not true. The rear brake rotor and caliper will hold a tire and wheel on if a rear wheel bearing fails. For a very short while, that is!

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  This photo shows a small bearing axle with the axle retainer, wheel bearing, wheel bearing retainer and the machined area that the oil seal rides on.  You can tell exactly where the seal rides by the shiny area around tthe axle.  This is the style of axle that our Classic Mustangs came from the factory with.


    While we're talking about rear disc brakes, rear wheel bearings can also affect their performance. If you read our last Newsletter article on front wheel bearings, you'll remember that loose front wheel bearings allow the rotor to wobble during use instead of running true. This causes the piston(s) in the brake caliper to be pushed further back into the caliper than it was meant to be. The result is that the brake pedal has to be pressed further to the floor before the brakes start to come on.
     Well, the same thing applies to rear disc brakes but in a different way. If the rear wheel bearing can move from side to side in the axle tube, it will allow the brake rotor to push the piston(s) in the brake caliper further back into the caliper just like loose front wheel bearings can do on the front. The result, just as on the front, is that you have to push the brake pedal further to the floor to stop the car.
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This photo shows a big bearing axle with the axle retainer/disc brake caliper mount, wheel bearing, wheel bearing retainer and the machined area that the oil seal rides on.  This example is from a Ford Granada 9" rear end with disc brakes.


    To check this, remove the rear brake caliper from the rotor and pull and push the tire and wheel back and forth. If you feel any in and out play, it's the rear wheel bearing sliding back and forth in the axle tube and it needs to be stopped. As you can see, on cars equipped with drum brakes, this movement presents no problem. More on this in our next Newsletter.
    How do you know when it's time to change your rear wheel bearings? Actually, it's pretty simple. The first hint will be a noise. A squeal, a rumble, a metal scraping sound. The sounds mean that the bearing is losing the grease that was in it and is starting to run dry. The louder the noise, the less grease is left. At this point, the bearing is generating heat, and heat is it's worst enemy. Heat can cause the bearing and the retainer to loosen up on the axle and it's bye-bye tire and wheel! 

   Now, before I have you believing that the wheels are going to fall off at any minute, read on. Although the problem should be taken care as soon as you become aware of it, usually you'll have plenty of time to replace the noisy bearing. The car will normally run for many miles before it leaves you stranded. But understand. When the problem gets to that point, the car stops. If you're 50 miles away from civilization, you'd better have a good pair of walking shoes and a fat wallet for the repairs!

     You'll need an axle, seal, and new brake shoes, at the least. The worst? That depends on how good you are at driving a car with three wheels! So if you're a person who gets used to noises and just keeps on driving, sooner or later you are going to face this problem. Guaranteed! Our good friends, the Eppersons, faced it with little or no warning on our trip in 1999 to the Mustang's 35th Anniversary Show in Charlotte, North Carolina. (See Mustang News starting on page 2 for a reprint of the article.)

   The other way you're going to know if the bearing needs to be replaced is to inspect it. You should inspect them if you're changing an axle seal, doing a major brake job, or changing the rear gear (3rd member, pumpkin, whatever term you're used to).

    You should also be sure to check them over if you're doing a complete rear axle change. The rear end is out of the car and easy to get to. When inspecting the bearing, first clean it off as best you can. Look for any sign of leakage of grease from it. Spin it around. Look again. If you see no signs of leakage, set the axle on a table or on the ground on the wheel studs with the axle splines pointing up. Now spin the bearing.


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To check the rear axle bearing, set the axle down on the wheel studs, then grab the bearing and spin it.  If the outer ring makes a complete revolution, it's time to replace the bearing.


    The outer ring should not make a complete revolution when spun by hand. If it goes around nice and easy, replace it. Because it is loaded with grease, it should have a lot of resistance when you try to spin it. If it doesn't have that resistance, it needs to be replaced. The grease is gone out of it and even though it may not have given you any sign it is going bad, it will start making noise soon.

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A typical rear axle seal.


  Lastly, when you change one side, do the other regardless of how the other bearing feels. When we had the shop here at Mustangs Plus, we did a lot of wheel bearings. When we only did one side, it seemed like it was no time at all until that customer was back to get the other one done. This has shown me that it's best to change rear wheel bearings on both axles at the same time. That way, you know you're good for 100,000 miles! 

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The housing where the rear axle seal is installed.


   Is there some other area that you need help in? If so, drop me a line at Mustangs Plus c/o Ron Bramlett 2353 N. Wilson Way Stockton, Ca. 95205 or email me at and I'll try to help! In our next issue of the Mustangs Plus Newsletter, we're on to rear ends! It seems that as the restomod craze sweeps the nation, many of our customers want to upgrade their Mustang with a 9" rear end, rear disc brakes, and lower gears for more umphhh off the line! What will work best for you? Check out the next Mustangs Plus Newsletter and then decide for yourself!

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