How Much Diff Oil is Enough?

[renovate7]

The book says 1.5 gallons per differential. This puts the oil right up to the edge of the fill hole. If I take enough out to get it 1/2" or so below the fill hole that is over a quart, maybe even two. That only leaves a gallon in the diff, way below what is called for. Is this OK, as long as I don't get into long drive/high heat situations? I can see that keeping the oil level down will stop there from being a large/constant amount of oil going thru the axle tube and ending up between the axle flange and outer seal, although there is probably always oil out there...Both my rear axles had a leakly wheel, even after thorougly cleaning the vents. I've already replaced the seals in the back axle and am doing the center soon. Good thing I check them as the bearings had been washed pretty clean by the oil. I drained and refilled the diffs, keeping them below the fill hole.

 

[patracy]

Been talked about many times and in the TM. Knuckle below the fill hole.

 

[M35A2-AZ]

I do one Knuckle below the fill hole.

 

[Westech]

I and everyone else over here in the box fills it up till it barfs out... install plug. we dont have time to jerk around with a interpretation of a TM. If the level was needed to be lower they would have drilled the hole lower.
Fill it up install plug.

 

[m816]

One knuckle below the fill plug. Or just fill it up."till it barfs, put the plug back in" and let the next guy change the seals as necessary. Along with cleaning the brakes form all the oli that soaks them.

 

[Westech]

Its your truck.. do what you wish. You will get 1000000 different answers on how to change a light bulb and 10X that on everything else.
I was just informing you what I do and how it has not failed me in 8 years of MV ownership and 20K plus miles.

 

[OverSizeHeavyHauler]

We service our own Heavy haul trucks, and we do the fill it til it barfs....your not going to fill the housing & axle tubes to the point where the breather/vent is blocked....(youd have to have the truck on its nose to do that...) Seal failures are 9 out of 10 piss poor installation...either the flange didnt get cleaned properly or somebody was in too much of a hurry and rushed it..

Ive had the Stemco classes on bearings and seals......they do fail, but if you half ass somethin, yer bound to fail.

 

[swbradley1]

The question was: How Much Diff Oil is Enough?

The answer: Enough to keep it from failing.

 

[tie6044]

One knuckle below the fill plug. Or just fill it up."till it barfs, put the plug back in" and let the next guy change the seals as necessary. Along with cleaning the brakes form all the oli that soaks them.

What does filling it up to the fill hole have to do with seals failing? If the breather is plugged then seals will fail from pressure. As stated above you are still not filling the tubes up so filling up to the hole should not matter.

 

[swbradley1]

What does filling it up to the fill hole have to do with seals failing? If the breather is plugged then seals will fail from pressure. As stated above you are still not filling the tubes up so filling up to the hole should not matter.

Kind of Westy's point.

 

[319]

The question was: How Much Diff Oil is Enough?

The answer: Enough to keep it from failing.

Was that on Jeopardy?


I go this depth below the fill hole:

 

[dmetalmiki]

Westech has it right. There's the hole and level sight. FILL to that. Simple.

 

[dmetalmiki]

I and everyone else over here in the box fills it up till it barfs out... install plug. we dont have time to jerk around with a interpretation of a TM. If the level was needed to be lower they would have drilled the hole lower.
Fill it up install plug.

Now THAT brought a (Much needed now'days)..Giggle..

 

[rustystud]

The question was: How Much Diff Oil is Enough?

The answer: Enough to keep it from failing.

I love "swbradley1's" answer the best.

 

[fleetmech]

IIRC the original fill level was up to the plug, but this was later lowered to "one knuckle down" to help reduce the chances of oil weeping through the hub seal. I cant remember the name of the publication it showed up in, but it was that military info mag... the one that often used comics/ drawings (often with a lady) to keep attention. I know that page has been posted here before.

On a brand new truck and/ or one with perfectly installed and well exercised seals, full is probably fine. Im guessing this fix helped reduce nuisance leakage and issues in trucks sitting in the base motor pool.