1976 Mark IV differential case color

[kdtbird]

After degreasing the differential I noticed that the differential gear case is not black like the rest of the differential. It is "primer red". i believe it is the original color because of the yellow paint mark. Can anyone suggest where to get the appropriate red paint color? What does the yellow paint mark mean? It also has 2 other paint marks (different colors) on the differential. Is there anything special about the paint/application method of these marks?

[action]

The seemingly random paint daubs are from final assembly workers used for a lot of different reasons. Either to identify a part (like the axle could be several different ratio choices and they look the same with out the paint daub) Or as a QC check - Or some other means like a color may be for a specific person. The markings are not necessarily specific to exact location or manner, just that they are there is significant for the use. An assembly plant is loud and many things are happening at the same time. A paint daub is a mean of communication.

Matcing the paint should not be difficult. Just make sure the paint is designed for metal. And the part is prepped for paint.

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[Dan Szwarc]

Primer red surprises me. On the 1979 Continental with 1000 miles it was natural, unpainted, steel, with an oil-type protection.

However, if you have carefully tried to determine the color by removing dirt, grime, etc. and red is what you find, then red it must have been (assuming that it wasn’t painted by someone else in the last 40 years).

[action]

I believe he is referring to the cast iron drop out section not the steel housing.

Clarity from the OP is need. Or a picture.

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[action]

Like these.

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[action]

A guess on the paint and color.

This paint or coating may have been applied by dipping after it was cast. Then the part was machined. If this coating is what I think it is I have used it with engine rebuilding. In addition to keeping the elements away so it does not rust, the coating allows oil to drain back faster. See the picture. Glyptal

If it is this coating it is not cheap. And for exterior use it serves no purpose as one is going for a look not performance. Just buy a good paint that is for exterior metal.

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[kdtbird]

Action, your picture shows the part I am referring to.
I can't get the difference to show in a photo now that the grease is gone. I used the water hose to remove the degreaser and left outside overnight to dry. It is now a nice uniform shade of rust.
Dan' post above got me thinking. The carrier housing has been removed at some time in the past. They used white silicone as a gasket. It oozed out uniformly around the entire perimeter of the carrier. That opens the possibility that it has been replaced or painted at some point, but it does have a yellow paint mark and has the sensor for the sure track brakes so I am inclined to think this is the original carrier assembly.
The axle code on the door jamb is "2", the tag on the diff is WGB_K 51C 75 9 455A
Guess I will never know for sure but Dan's original is probably what is correct.

[action]

I believe an axle code of 2 = 2.75 ratio conventional axle. (data from my '71 shop manual)

From the metal tag:
Top row of WGB K 5 1C
Bottom row (Missing 2) - 75 9 455A

Top row:
WGB-K5 axle style
1C and missing??? is the date code. Likely the 1 is a 7 which would be 1977, C = March

Bottom row:
Missing 2 75 is ratio
9 = ring gear size

I forget what the last number mean.

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