63 12 Bolt Rear Bearings and Shims

[rbruno68]

I took my rear apart to have it cleaned and a new posi added and when I pulled the bearings out, I had a shim come with it. I have read at least a half dozen threads or more on the forum that talks about the shim. The picture below has the shim, the old bearing race and new bearing. I can't say that the threads came to any conclusion on what the shim is for and if it is needed. I took some measurements and the Shim measures .063 thick. The new bearing is .816 thick and the old race is .825 thick. So if I use the shim, it won't push the bearing out any further then the original because the new bearing is slightly thinner. My old race diameter is 2.528 and the new one is 2.535, so slightly bigger. With as easy as the race came out, I think a little more crush wouldn't hurt. I bought new Moser axles because I went with posi and needed the 30 spline axle. I don't have an issue with a worn axle where the bearing or seal will ride. The seal looks different then the original, but it has crush in the axle tube, so I don't think that is an issue. But, wondering if I need that shim and what is the purpose?

[Accelo]

.007 thousand is not a little more, it's a bunch for something a nominal 2.5" in diameter.
It will require tons of force to install this and will likely reduce the internal diameter so much that the axle will not install with the necessary diametric clearances.
" With as easy as the race came out, I think a little more crush wouldn't hurt", you need to measure the bore to get the exact interference fit.
Typically, it would be in the order of .0005 per inch in diameter. I would expect to see .0015 to .002 interference fit in most applications, with this diameter.
I suggest you look for a better/different bearing.
I have experienced this issue before. I'm glad you identified the size issue before the installation. In my case, I did not identify the fitment issue, the first time I did this. I believe they are just substituting another "close to size" bearing.
There is no way a bearing manufacturer would be this far off in sizing.

Since this is a straight roller bearing, no shim is necessary. Seems more like a splash shield than anything.

[rbruno68]

Originally Posted by Accelo

.007 thousand is not a little more, it's a bunch for something a nominal 2.5" in diameter.
It will require tons of force to install this and will likely reduce the internal diameter so much that the axle will not install with the necessary diametric clearances.
" With as easy as the race came out, I think a little more crush wouldn't hurt", you need to measure the bore to get the exact interference fit.
Typically, it would be in the order of .0005 per inch in diameter. I would expect to see .0015 to .002 interference fit in most applications, with this diameter.
I suggest you look for a better/different bearing.
I have experienced this issue before. I'm glad you identified the size issue before the installation. In my case, I did not identify the fitment issue, the first time I did this. I believe they are just substituting another "close to size" bearing.
There is no way a bearing manufacturer would be this far off in sizing.

Since this is a straight roller bearing, no shim is necessary. Seems more like a splash shield than anything.

Last night I went home and tried to measure the inside diameter of the tubes. I don't have a really good caliber to measure the inside, but with my weak skills at measuring, I was coming up with 2.531 to 2.533. I was trying to measure in different places, but I can't imagine the tubes our of round, but they are 60 years old.

I also did some searching on line at different rear end parts distributors and the regular Classic Parts, etc. All were saying that the 63 rear uses a 2.535 bearing.

I should have taken another picture of the bearing because the bearing also now looks like it has a slight step in it on the outer race. One side is very slightly smaller then the other side. Not sure what that is about, but the one side does start a little easier into the tube when I just put in there by hand.

Since, I am having an issue measuring, does anyone know the correct diameter of the axle tube or what size bearings they were able to find?
Rob

[rbruno68]

Here is a side shot of the bearing and you can see the slight line where the race is a little smaller on one side.

Has anyone had this in the bearings or an issue rebuilding a 63 rear?

[Grounded63]

I have a '63 rear end that is apart. It has Hyatt, U S made axle shaft bearings. The OD. mic's at 2.5315"

-EDIT - measuring the housing bore with a dial bore gage. I come up with an average of -.0005 to -.001" of the bearing OD. Or 2.5305 to 2.5310".

That smaller OD. step. Helps to start the bearing straight/square to the bore. The Hyatt's do not have that feature.

Do your new bearings have a brand or part number etched into them ? Because, you should be able to look up the spec for them.

[Grounded63]

Originally Posted by Accelo

. There is no way a bearing manufacturer would be this far off in sizing.

I recently needed to re-bearing an electric motor. The replacement Timken bearings were something on the order of 0.023" undersized on the ID. For identical part numbers. But, they are made in Mexico now . . .

[rbruno68]

The bearing is KOYO DB 68126. According to the info I could find it has a 64.3MM OD which translates to 2.531496 inches. It could be just that my measurements and instruments (more likely me) were off on measuring. I think these may be ok.
Rob