Foamy differential oil v. bubble-less

[oifvet]

When changing out the differential lube in my M35A2 recently, I notice something odd about the oil in the front differential. Keep in mind, the truck had not been driven for over a week when I did the change.

Working forward from the rear-rear diff, the (old) oil that drained was black/brown and smooth in appearance. NO bubbles. Same with the forward-rear differential, black/brown, smooth, no bubbles.

The front differential was a little different. The oil that I drained was not so dark. Almost a brownish green. Now that part I figured was just "newer" (less used) oil that kept its integrity. (The front (steering) axle is an air-select, not a sprag). What I did find odd, was how "frothy" the oil in the front differential was. It was like a foamy drink of some kind. Nothing like the other differentials that I had just drained.

Maybe not something to get concerned about, but I found it odd. Especially after having sat for over a week, and even then, the front axle was never engaged. What could be agitating the oil? I would expect to see the froth if I had drained it after a drive on the axles that were in use. Anyone know differential oil properties and what might cause this?

 

[FreightTrain]

Not sure on the froth but the front axle is always turning.The only thing disconnected is the drive from the transfer.The driveshaft and chunk are still turning when the truck is moving since the axles are splined to the hubs with no lockouts(unless installed aftermarket).

 

[Kwai]

Water in the oil will turn it a brownish color. The water/oil emulsion also tends to froth easier, the bubbles you are seeing.

 

[oifvet]

I wondering if the oils in all three diffs were even the same. Hard to tell. I drained the two rears into one pan, and the front into a separate pan. That's how I was able to see the differences. The trans and transfer case were the coffee brown color, much like the two rear diffs.
The oil changes went well. I spilled NONE! Gotta love that! I get the feeling the oil in the rear two diffs was long over-due. I definitely put more oil back in, than I drained out. Nothing was dry, but I'd say the oil had lost most of its properties. I'll keep an eye on them. I may just pull the filler plug from time-to-time and see what it's looking like. I can always put a pump or two in to bring the level up a bit if need be.
I will say, investing in a good, strong hand pump that went on the 5 gallon bucket was a fine move. WOW! I could not imagine trying that with one of the cheap ones from the auto parts store. I found a good one at Harbor Freight Tools. The hose had enough length to reach all the fill points and I was able to pump the handle from outside the truck, (not underneath). The end of the hose had a nice "hook" shaped aluminum tube that stayed inside the filler opening. It also had a spring-tension against a ball valve which worked as a nice shut-off. I think I paid $29.00 for it.

 

[amanco]

Speaking of oil / air entrapment. Here is an interesting article on oil additives with lots of interesting oil info on the home page. Waht kind of additive may have been in your front diff?

http://www.bobistheoilguy.com/images/lucas/lucas.htm

 

[oifvet]

Interesting. I would not know about any additives before I bought the truck through GL. It was at Camp Johnson, Vermont Army National Guard. When I replaced the oil in the diffs, I did not add anything.
I am a Lucas fan. I believe it is a well engineered product that doesn't target a broad market like many additives on the info-mercials. I have no synthetics of any kind in any of my vehicles. There has definitely been a marked performance improvement in my 49 Ford w/ flathead 6, since adding Lucas to the fuel and oil. Very smooth and reliable operation. I don't believe you can "fix" a vehicle with anything in a bottle. But, I do believe you can improve performance under certain conditions, depending on the product and application. So far, the only additives I've used in vehicles that I own have been Lucas' (oil stabilizer and fuel stabilizer), and Sea-Foam (fuel dryer / injector cleaner).