Grease plug for steering knuckle (1 Viewer)

[IdahoDoug]

Perk,

The steering knuckle is a fairly complex and well designed structure. The waterproof function of the grease is twofold. It is both a physical barrier to water, and it maintains the lip of the rubber/felt seal on the steering knuckle that drags back and forth across the spherical axle housing bell. To do this, it must constantly weep a bit of grease that moves grit and contaminants away. In a very real sense, the grease is constantly flushing out of the rubber/felt seal in slow motion. This was designed for a harsh offroad environment.

Since the structure is literally designed to leak slowly, the square plug is there to replenish the steering knuckle. A half dozen squirts from a hand grease gun each oil change is about right to replace the amount of grease that has wept out over 5-7000 miles.

While we're on this topic, I occasionally see birfields that are dry on the outside, but full of grease. What has happened is the felt has become so contaminated or caked with mud that it is swollen and dried and not allowing the rubber lip to deform as designed, so little grease comes out. You WANT grease coming out. The 97 I just bought was like this - the knuckle is full of grease and the birfield is silent. But the outer bells were dry. So I soaked the seals with white lithium grease for a few days, then brushed them lightly with a toothbrush to encourage the felt to release what was dried dusty crud. Now my seals are properly weeping again and the bells are lightly greased. So check yours and consider this action if the outer bells are dry.

DougM

 

[perk]

Doug,

I apprecitae your educational posts. I was getting hung up thinking that the birfield and knuckle chamber were the same. Where on Raven's diagram is the knuckle chamber?

 

[IdahoDoug]

Hmm. Kind tough to define as that diagram seems to be slightly tighter dimensionally than the 80s. The tulip shaped bell on the outer axle (right hand piece 10" long or so) is the birfield chamber. It is fully inserted into the steering knuckle chamber. To roughly define the steering knuckle chamber, imagine the center of the splined section inside the birfield chamber as the center of a clock. From that center point, the steering knuckle chamber starts at the black void at 4 o'clock, and goes clockwise to the 2 o'clock position. All the dark voids therein are inside the steering knuckle. Obviously, the axle seal separates the steering knuckle grease from the differential gear oil in the axle housing. There are some good pictures on the Slee site of a repack process, I believe....

DougM

 

[perk]

Thanks Doug,

Nice description, got it. I see what you mean, from the looks of that diagram, it certainly does not appear that grease through the square plugs would reach the birfields, regardless of how much they spin. I'll be repacking the birfs this weekend (no small task for myself) and am accumulating as much knowledge as I can beforehand.

Perk

 

[IdahoDoug]

Do some serious cleaning of the steering knuckle/axle ends/hubs beforehand and you'll be glad you did.

DougM

 

[RavenTai]

the plug is fairly close to the ABS sensor, and they are in the same chamber,

 

[Rich]

For the grease added through the plug to exit through the knuckle seals it has to pass by the birfield. This flow does happen, as evidenced by increased grease exiting through the seals after adding grease through the fill plug.

I remain open as to whether or not any of this grease moving around migrates to inside the birfield. The test I proposed is simple and would answer the question. I have seen some fluorescent blue grease that I expect would show where grease added through the plug eventually ends up.

 

[IdahoDoug]

Rich,

Actually, the grease doesn't have to flow by the opening to the birfield chamber. There are all manner of other ways it can move, but the important thing to consider is that grease going past the opening of the birfield chamber does nothing for the birfield. If grease were being flushed THROUGH the birfield - actually displacing old with fresh - then we'd be on to something. I agree the test is a simple one, and I'm planning to do mine this summer so if you find a bright grease I'll put a tube in soon so when I open it we'll have a data point as I think the exercise is definitely worth doing. Since I tow a heavy boat starting in a couple months, I'll have some higher than average peak hub temps, which would maximize any grease thinning/mixing potential. See if you can find something that will contrast with the Amsoil dark purple in there. Blue would be great, as would a bright red like the Mobil 1 stuff.

DougM