Differential Oil Sample

[rfitzpatrick]

I put 300 miles on a rebuilt Differential, and did an oil sample test.
It came back: 47 ppm Silicon, it's listed in Red on the results report.
What should I do next, plz?
Tks

[SwampLedge]

https://www.machinerylubrication.com...con-oil-source

[MALAK]

I just did a quick Google search for sources of Silicon in oil analysis.

https://www.machinerylubrication.com...sources-in-oil

1. Defoamant Additive — Many oils contain defoamants based on polymeric methyl silicone. Because silicone contains the element silicon, the presence of this kind of additive will show a positive silicon reading in spectrometric analysis. The typical levels of silicon seen under these conditions are around 1 to 10 ppm.

2. Silicone-based Sealant — Many sealants used for industrial and mobile applications are silicone-based. The level of silicon observed will, of course, be directly related to the amount of sealant leaching into the lube system.

3. Casting Sand — Some components are made by casting in sand (silicon oxide). Although new components are cleaned thoroughly prior to installation, it is not uncommon to see 50 to 100 ppm of silicon from new equipment. This level should drop as the component breaks in and regular oil changes take place.

4. Coolant Contamination — Many engine coolants contain inhibitors that contain silicon. In an engine application, high silicon readings in conjunction with other elements such as sodium, potassium and boron may indicate a coolant leak.

Without other evidence, differentiating between additives, silicone and casting material as the source of silicon is difficult. However, dirt ingression can be determined by tracking both silicon and aluminum. For most common dirt, which contains the minerals silica and alumina, tracking silicon and aluminum, which should show up in lock step trend in the ratio 3.4-to-1, can be used to confirm dirt regression.

Of this list it seems #1 and/or #2 would be the most likely sources of Silicon but without more info, like brand and type of oil or was silicone sealant used it's hard to tell. Maybe change the oil, drive a bit and re-sample.

[katy]

Did you use new oil in the rebuilt differential? If so, how much silicon is in the new (unused) oil?

[rfitzpatrick]

Club member rebuilds differentials, the member whom installed/serviced has moved, so I'll need to contact him for that info. I've replaced that oil and used Mikes AFordable Vendor for reservicing W-600, and will do another 300 mile sample.
Tks

[Patrick L.]

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Yep, just fill and drive it. A good 140W [or 90W] will work just fine.

[Tom Endy]

The 600W oil the Model A suppliers sell is all different, depending on who you buy it from. My preference is what Bratton's sell. It is a heavy Shell oil with 25% STP blended in. It is an amber color and does not foam and does not stink, like some do. I recommend it to all my customers I rebuild differentials and transmission for, if they ask.

I rebuilt the rear axle assembly in my Victoria 25 years ago and have since put 52,000 miles on it. Just recently I changed the oil in the differential, for no other reason than I could.

I have driven several modern cars over 100,000 miles and never changed oil in the differential.

Tom Endy