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Rust line inside front Differential.

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Old Apr 14, 2018 | 02:57 AM
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Question Rust line inside front Differential.

How does that occur?
Do to the condition of the paint and interior, I assume that my 78 sat in a garage somewhere for a LONG, LONG time.
Shortly after I purchased my 78 I put it through an off-road test. It passed with the only casualty being that the front axle seal failed. When we removed the pumpkin cover, we noticed a rust line inside.
Thoughts?
 
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Old Apr 14, 2018 | 06:06 AM
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Oil floats on water but condensation can form from the air above the oil. This leaves the rust line. At least that's my guess.
 
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Old Apr 14, 2018 | 08:14 AM
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^x2 condensation from sitting
 
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Old Apr 14, 2018 | 12:52 PM
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X3 on condensation from settin' around...and not being used often.

Same thing with a little "milky oil" in the valve cover/valve train/
 
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Old Apr 14, 2018 | 08:49 PM
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Which is exactly why the Ford owners manual states to drive the truck with the hubs locked once a month to keep things churned up inside.
I also run it in 4wd with the hubs UNLOCKED to move things around that way as well.
As long as you're running one OR the other, rather than both locked together on the street, you can run on the pavement for extended periods.

That "not on pavement" thing about 4wd is not as big a deal with F250's and 350's where the front and rear diffs are both Dana and have the same gear ratios, but it can be a very important thing to avoid in a Bronco or F150 where the front end is a Dana and the rear is a Ford 9" and the gear ratios rarely, if ever, quite match up. Binding can result on high traction surfaces.

Anyway, sorry for the rambling truck talk. Many don't have the old Ford books that came with their trucks anymore, and may not have grown up in the time these were new, so it's not always known to lock things in sometimes to keep them happy and dry.

Oh, and while your'e at all this, make sure the differential vents are clean and not plugged up.
And for future reference, any time you spend much time crossing streams, or a heavy winter full of snow, or whatever moist environment your truck might live in, it's not a bad idea to change the gear lube when a lot of moisture is a thing. Maybe you don't have to change it every year if we're simply talking humidity, but if water is part of life where you are then changing it out more often than normal is not a bad idea. At the very least you should lock the hubs in now and then and drive normally that way for awhile.

Paul
 
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Old Apr 27, 2018 | 01:44 AM
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Originally Posted by RKDxpress
Oil floats on water but condensation can form from the air above the oil. This leaves the rust line. At least that's my guess.
How long would you estimate it sat for this to occur?
 
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Old Apr 27, 2018 | 01:47 AM
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Originally Posted by LONCO
^x2 condensation from sitting
How long would you estimate it sat for this to occur?
 
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Old Apr 27, 2018 | 01:47 AM
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Originally Posted by 1TonBasecamp
Which is exactly why the Ford owners manual states to drive the truck with the hubs locked once a month to keep things churned up inside.
I also run it in 4wd with the hubs UNLOCKED to move things around that way as well.
As long as you're running one OR the other, rather than both locked together on the street, you can run on the pavement for extended periods.

That "not on pavement" thing about 4wd is not as big a deal with F250's and 350's where the front and rear diffs are both Dana and have the same gear ratios, but it can be a very important thing to avoid in a Bronco or F150 where the front end is a Dana and the rear is a Ford 9" and the gear ratios rarely, if ever, quite match up. Binding can result on high traction surfaces.

Anyway, sorry for the rambling truck talk. Many don't have the old Ford books that came with their trucks anymore, and may not have grown up in the time these were new, so it's not always known to lock things in sometimes to keep them happy and dry.

Oh, and while your'e at all this, make sure the differential vents are clean and not plugged up.
And for future reference, any time you spend much time crossing streams, or a heavy winter full of snow, or whatever moist environment your truck might live in, it's not a bad idea to change the gear lube when a lot of moisture is a thing. Maybe you don't have to change it every year if we're simply talking humidity, but if water is part of life where you are then changing it out more often than normal is not a bad idea. At the very least you should lock the hubs in now and then and drive normally that way for awhile.

Paul
How long would you estimate it sat for this to occur?
 
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Old Apr 27, 2018 | 07:45 AM
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Originally Posted by Animal1978
How long would you estimate it sat for this to occur?
Out in the air, surface rust (that can be eliminated with a brush of yer hand) will show up overnight.

Semi airtight metal..such as in the differential....eh, give it a week of non use before a rust line will start.

If your thoughts are along the lines of rust > scales > pitting > holes, well that takes months to develop.

You also have a bunch of variables in the "rust to hole in the metal" such as temperature swings, humidity, elevation, fluid levels, an outdoor garage or not, etc.
 
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Old Apr 27, 2018 | 01:59 PM
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^x2 my best guess
 
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