MGB: Kingpin seal

This is bad right? New seal in order?

When I get these apart is there any thing else I should to to them. I was thinking I should do both sides. There was a lot of grease all over these, probably coming out of this seal. Did it bust because someone shot too much grease in there?

Thanks for any advice.

Once you get all the old grease and gunk out you can check the tolerances.

Not so devestating!
Clamp the assembly in a vise and check play vertically and side to side.
But if you're going to take them apart, yes replace the seal. It looks to me that it's the wrong one anyway.
They usually arent visible as they sit deep in the cup under the dust tube.
RS

Thanks, Robert. I will do that.

It's just a dust seal, so long as it's in place and not binding anything then you can leave it alone. If the swivel assemblies are off the car and apart already then this would be a good time to replace it though, so if that's the case then I'd do it just to save the effort later.

Brandt,

Don't worry about that seal. It's just a square section O-ring that works as a dust seal. Check out the swivel axle first (instructions below) to see if you even need to think about worrying about that seal. To replace it you need to dismantle the swivel axle, and that is hard to do - real hard. " ... Because someone shot too much grease in there?" No such thing as too much grease in there, in fact if you can pump grease into the zerk in the picture and watch grease come out of there that is a good sign.

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How to check a swivel axel on the bench

To check a swivel axle that's off the car for wear put it in a bench vise by the caliper mounting lugs. The kingpin should turn freely by hand without being excessively free. To the unpracticed hand this is probably not helpful, but try to imagine how it would feel it were just a bit more free to turn than if it was binding at all. Then try to move the kingpin back and forth along the long axis of the kingpin. Factory book spec for this endfloat is 0" to .002", This actually is the sum of all the clearances between the top of the swivel axle, the bottom of the upper trunnion, the bronze thrust washer, and the two shim washers. You're seeing if there is wear on the bronze thrust washer and/or the shim washers. For "hand feel" reference, when greased you should not feel any movement in this direction. In my judgment, "worn but not worn out" would be 4 or 5 thou, but I'm in the practice of making these better than new so that figure may be too much or last a gentle driver a fair amount of time. What I know for sure is that these parts of the swivel axle are nearly always the LAST to wear out.

With the swivel axle assembly still mounted the same way, try moving the kingpin back and forth in the swivel axle, in line with the same axis as the stub axle (the part where the wheel bearings go). Basically swinging it from the upper trunnion to check for wear in the lower of the two swivel axle bushings that the kingpin rides in - the lower one wears long before the upper. As built, there is almost no perceptible play here, and none with grease in place. Numbers wise, probably .0005" or less (I go by feel when I'm building them), just enough for the kingpin to freely move. Checking for play in the axis 90deg from the stub axle, you generally will find little to none. The lower swivel axle bushing and that kingpin area is generally the first or second part of the assembly to wear and one of the two worn swivel axle parts that give bad (at best) handling.

MANY swivel axels get filled up with hardened grease that can give false results to this check. If you try pumping grease in and do not see new grease coming out by the dust tube you need to heat the swivel up with a propane torch so you can melt out the old grease. Odds are, if grease hasn't been able to get to the bushing and kingpin, things are worn out. If anyone wants, I can take a picture or two of kingpins that might have seemed ok but in fact were rusted, pitted and abrading the bushing. Moving back and forth showed little movement, but that's with a human arm moving things, how about with a couple thousand pound moving car? Hard grease can do "amazing" things. In my judgment, if the bushing and kingpin are not worn much to the eye, "worn but not worn out" would be about .001-.003" movement. Wear here accelerates exponentially, so if you give it an inch it will take a mile. If the bushing and kingpin are worn much to the eye, they are worn out.


Last, check the kingpin bushing that the distance tube runs in. This area is the other wear spot that wears either first or second in the assembly, depending on where grease starvation occurs first. Its also the spot that has the most dramatic and potentially dangerous effects on handling when it goes bad. There should be the same degree of play as in the kingpin/swivel axle bushings. Check with a known good distance tube. If you find more wear than can be barely felt, it's time to fix it. If the kingpin is ok other than a worn lower bushing, its possible to fix it by rebushing the kingpin, but in practice more than 95% of the kingpins are junk. If the distance tube bolt would not come out of the distance tube when the front was being disassembled, odds are excellent the bushing is worn.

If anyone has any questions, feel free to call or email if you don't want to post.

708-752-1701

Grease squeezing out is not a sign that the kingpin assembly is bad. You will get grease oozing out when you lube the assembly. It may be bad or okay, you have to check for movement, tolerances, etc.

Thanks Wade ! good information, any specific grease you use ?

Dave '79 MGB

Wade, that's reall good stuff. Saved me a lot of aggrivation for sure. Peter, your's is artwork.

Thanks all for the advice.

Brandt '73 MGB

You're welcome. Regarding grease, I use Valvoline red grease. I can't think of the exact name, but its spec'd for wheel bearings, foreign cars, higher temps, extreme pressure and wear resistance. I just go to the familiar spot on my parts place's shelf and grab a bunch of tubes. Nothing too exotic about the grease requirement for these, just that you do it frequently and make sure it flows everywhere it should.

Wade, your reference on checking swivles above neeeds to be added to the library. I went through my swivels last week and found the information invaluable. Thanks for taking the time to write it up.

Thanks Brandt