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Scored differential bearing bores (55 Packard)


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Posted (edited)

Hi,

 

The side bearing races on my differential are somewhat scored up. How can I fix this? 

 

The left half is threaded (normal) whereas the right half is the scored bearing race. The other side is not as bad.

 

FYI this uses a Timken 25590/25520 bearing, in case you are wondering about dimensions.

20240605_205737.jpg

Edited by human-potato_hybrid (see edit history)
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Here is a thought to consider.

 

I have accidentally made similar marks when machining parts on my lathe. I'm only an amateur machinist and sometimes make mistakes. When turning or boring a part the tool feed is a fine pitch for a slow thread even cutting, then when retracting it the tool is moved faster with a coarser feed rate. Sometimes there is still some residual pressure on the cutter which produces a "scar" very similar this this. I have had this happen most often when using a boring bar that can sometimes be a bit light and the boring bar can bend slightly under the pressure of cutting. Then it springs back slightly on the way out creating the "score" mark.

 

If you look closely and the scoring looks slightly like a spiral and especially if the marks are evenly spaced then it may only be a residual machining mark from the factory. If you have a thread gauge to compare and it lines up to a standard thread pitch then that would support the theory. In this case it does look very similar to the thread pitch for the adjusting nut beside it.

 

If there was actual scoring from bearing problems, then the outside if the bearing race would usually also show some marks.

 

I have also seen similar marks on some early bolts that were made by machining the bolt and threads instead of rolling them the modern way.

 

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Put the outer bearng race in and tighten the clamp. If it holds the race tight you have no issues. 

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On 6/7/2024 at 5:12 PM, Oldtech said:

Put the outer bearng race in and tighten the clamp. If it holds the race tight you have no issues. 

Ok I will test that when I'm back at the shop later this week. I will have the new bearing by then too.

 

If it's a bit loose, what about Plastigage ing it and buying some shim stock to match? e.g. if it reads 2 thou then wrap around with 1 thou shim stock.

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Posted (edited)
On 6/7/2024 at 5:12 PM, Oldtech said:

Put the outer bearng race in and tighten the clamp. If it holds the race tight you have no issues. 

Ok I got the new bearings in and this is correct. I would describe it as a light interference fit. My concern is they have some preload on them when the diff is reassembled. What do you think?

 

The preload procedure is described on the left paragraph of Page 7 here:

https://packardinfo.com/xoops/html/downloads/servicemanual5556/Sect15_RearAxle.pdf

Edited by human-potato_hybrid (see edit history)
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