Rear Outer Hyatt Bearing Fit

[Dan B]

I am test fitting the rear axle outer bearings during a rebuild. I have new axles, new (“best quality”) bearing sleeves, and bearings that are essentially NOS. They do not just slide in like I am accustomed to and take small taps from a rubber mallet to fully seat them. When they are half way in, the axle turns freely and the rollers spin. Once they are fully in, the axle spins freely with no binding.

Is it normal to have to tap the bearings into place? I am used to just sliding them in and out but wonder if that’s because everything was worn out.

[RajoRacer]

I have found that with new axles, sleeves and really nice used bearings are a bit tight ! I usually measure my bearings to have a few thousands wear to slide in nicely with the new Lang's B.Q. sleeves.

[MWalker]

My experience is similar to Steve's. With new axles and sleeves, sometimes you'll need rollers worn about 5 thousandths (or even more) in order to get them into place. I suspect the sleeves are slightly thicker than the originals but don't know for sure. Good bearings with a little bit of even wear aren't too difficult to find, so I haven't had any problems doing it this way.

[Dan B]

Thanks guys. In your opinion, is there any harm in using a better bearing with a tighter fit if I can get them tapped into place? How tight is too tight? I figured they would wear in a little bit after use but I don’t want to cause any problems going down the road or not be able to get them out to service them later on. I have bearings with worn rollers, but they have other problems too.

Steve, the bearings I’m using are the primo ones you sent me!

[John Illinois]

I used an Ammco cylinder hone. I found the sleeves to be right thickness but uneven surface. That gave a nice sliding fit.

[Adam]

“Wearing in” anything like this is essentially going to be displacing or wearing off metal that is an interference fit. Does that “worn away” metal just disappear? NO! It just rolls around in there and recirculates between the bearings, sleeve, and axle shaft. Some of it will abrade and some of it will embed. Bottom line is you don’t want it to happen.

Will it cause an early failure? Maybe. If you drive 100 miles per year it’s probably not worth worrying about. If you want the rebuilt axle to last 12,000 miles or more, then you need to have a nice, interference-free fit.

I made a fixture that is a heavy steel tube that was bored, hardened, and finish honed to exactly the FORD blueprint spec for the bore in the axle housings. It is hardened harder than the sleeves so pressing sleeves in and out will not scratch or wear it. I use only the “best quality” sleeves and when I install ANY ONE of those sleeves in the fixture and check the inside diameter all over the inside of the sleeve, there are areas inside the sleeve that are generally about .008” too narrow and areas that are maybe .004” too wide. My procedure is to hone each sleeve on a Sunnen Horizontal Honing Machine until the narrowest spots inside the sleeve equal the diameter of the shaft journal plus 2 times the largest roller diameter. The final check is to slide the sleeve that is in the fixture over the actual bearing and axle shaft and then spin it. It should easily slip on and off the shaft and should spin several seconds on its own until slowly coming to a stop and sometimes even reversing direction a little as the fixture isn’t perfectly balanced and maybe weighs a few grams more on one side.

Another fact to consider is that I’ve seen quite a few FORD axle housings that have oversize bores. Generally the oversize will be right at .008” which makes me think there might have been fairly regular “production errors” on either sleeves or housings and the opposite part was made oversize/undersize instead of scrapping stock.