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MG MGB Technical - Quickest way to change King Pins?

MOT failed today on OS king Pin play.
I will buy a complete assembly but what is the quickest and easiest way to change the unit?
Do I need to remove the road spring or can I just support the bottom of the spring pan?
Any advice would be welcome!

Cheers.
AdrianS

Just support the bottom of the spring pan. Make sure the car is safely supported elsewhere on axle-stands, and just use a jack to raise the pan until the damper arms just come off their rebound rubbers.

Tie the caliper up, don't let it hang on the hose. You should really use new lock-tabs when refitting.

You may have to hacksaw through the upper trunnion pin as it is unlubricated and two I have had to remove (one king-pin and one damper replacement) had totally siezed to the inside of the sleeve in the rubbers. Undo the damper arms clamping bolt and wedge the arms apart to make room for cutting through the pin so as not to damage either king-pin or damper arms. You will probably need to do this to get the new bushes between the arms anyway. Use Waxoyl or rubber grease to aid their insertion into the trunion.

Get upper (bushes, special pin and nut) and lower (bolt, sleeve, shims and grease seals) fitting kits. Check the holes in the A-arms haven't ovalled, which happens if the lower nut isn't tightened properly. Make sure you get the proper low-profile castelated nut for the upper pin, kits for some time were being sent out with Nyloc nuts which are totally inadequate as the end of the pin barely engages with the nylon insert.

You *shouldn't* have to change shims in the wheel bearings if they and the hub go back on as-is, that is if they were shimmed correctly to begin with. You will certainly have to check the end-float and make sure it is correct, so consequently may need some shims, it is vital to get this correct.

Needless to say use the correct torque for all bolts, especially the hub nut.
Paul Hunt 2010

Adrian. To add to what Paul has posted, you need to know why the kingpin failed--is it a problem with the kingpin itself or with the bushings in the stub axle? Most commonly, the kingpin is fine, if it has been kept lubricated properly. I have replaced the kingpins on the three family MGBs over the years. On two of them the kingpins were in very good condition and measured the same diameters as the new kingpins. The only kingpins which could not have been reused was the vehicle which has been stored, outside for over ten years, with a seized engine. Those kingpins showed rusting inside the dust tubes.

The most common cause of problems with the kingpin/stub axle assembly is the wear of the bushings in the stub axles. The old bushings in the stub axles need to be pressed out and and the new bushings need to be pressed in using a piloted drift and a hydraulic press. Then, the bushings need to be align reamed using the special reamer sold for this specific purpose. Often less expensive to purchase reconditioned stub axles than to purchase the reamer for a single use.

Les
Les Bengtson

I once had an MoT failure due to vertical play in the kingpin, so you really do need to know what the failure was for?

In my case, I was able to shim the top trunnion to achieve the correct play.
Dave O'Neill 2

The King pin had about a 1/4 inch play when pulling and pushing the wheel (the MOT tester showed me) at the bottom of the pin. Must admit I have not noticed a problem with the steering or felt any knocks when driving the car! Just got 10 working days to get the problem fixed or I have to pay for a full re test!
AdrianS

If it is the bottom that is moving make sure it isn't simply the bottom bolt loose, which may have ovalled the A-arms and cut into the pin. In this case the whole of the bottom trunnion will be moving back and fore. Changing the king-pin and swivel-hub assembly will do nothing for this, simply tightening the existing bolt will 'cure' it, although the A-arms and bottom pin should be replaced.

If it is the king-pin bushes that have worn the trunnion will be static and it will be the swivel hub that will be moving relative to it.

1/4", depending on where it is measured, sounds more like A-arms than king-pin.
Paul Hunt 2010

I will report back tomorrow when I have had a good look and start dismantling!
AdrianS

Adrian - releasing the spring tension is only a matter of putting the car on axle stands under the chassis (which you'd do anyway), supporting the pan with a jack, removing two of the pan bolts, then slowly releasing the jack. Once you've done that you can be certain that it won't explode while you're pulling it about. An extra few minutes on the job for total safety is well worthwhile.
Miles Banister

Another myth - it is physically impossible for the spring to "explode" - it is too long to get out of the upper & lower mounts before all the tension is gone and the lower mount is swung almost vertical.

If the anti roll bar link is still attached then it takes some considerable force to swing the arms far enough down to get the spring out.
Chris at Octarine Services

Even with the rollbar drop link disconnected (which was the only way I have been able to remove springs of three different types on two cars) the arms have to be pushed down quite a bit to get them in or out. In fact with the longest springs I'm pretty sure I had to undo the two front pan bolts as well as push it right down to do it. As long as there is a trolley jack under the pan the spring won't be going anywhere.
Paul Hunt 2010

Checked today and it is definately the Stub axle moving. The bottom trunnion is solid with no movement at all.
It is a bit annoying really as I have just found a receipt from the previous owner and he had both sides replaced july 2008 not long before I had the car. Don't know why the lower bush in the stub axle had failed as everything was well greased. I suppose knowing that they are recent replacements and the car has not done a lot of miles will hopefully make disassembly a bit easier!
AdrianS

That's bad. I did have to replace one on my roadster not long after buying it over 20 years ago, but that was 40k miles ago and the V8 has done 75k so far on the ones it came with. Were they completely replaced? Some people rebush and ream, which has its own problems and potential for taking too much off, I'd replace complete every time. I do grease every 3k, have three nipples on each, and I make sure grease comes out of the seals on the top and bottom bushes and the trunnion ends.
Paul Hunt 2010

This thread was discussed between 27/05/2010 and 31/05/2010

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