King pins swivel axle and bushes

I bought the MGB as a usable, running, legal and roadworthy car. Well its running (just) and legal, but that last one does stretch the trade descriptions act a little. Anyway this means I'm going to have to do more work on it than I had envisaged. One complication though is that for various reasons; largely to avoid annoying the residents, I have agreed not to put any more dead and immovable cars on my drive. This means that anything I do on this car has to be done in one day- drive-in and drive-out. Bit of a problem for me as I tend to work very slowly....

I don't think there is any way I can strip the stub axles, remove kingpin bushes, clean, renovate and refit with new wheel bearings in a single day. Even more so as domestic taxi arrangements often shorten my time available anyway! The solution is to use exchange units... but (glutton for punishment) I don't really want to do that, I wouldn't learn as much about the car, so I would like to do this myself. The solution to my mind was to buy two used stub axles  and a single hub (Andy Jennings MG Spares) so I can recondition them- effectively to prepare my own "exchange unit" before fitting it to the car. This is really a learning curve-it keeps me off the streets (?) but I'm not going to pretend its cheaper- in fact many king pin kits are more expensive than the exchange parts from MGOC - and that's my fallback position if this all goes pear-shaped! However, this approach means that I will be experienced and tooled up for this particular job ... and although this is my first kingpin swap in an MGB, its actually my fourth overall so its probably now worth making it as easy as possible.

I received the two used units promptly and set about cleaning them up. They came with top trunnions and dust-shields. I stripped the kingpin castellated nut and removed the kingpin and trunnion, detaching the dust-shield. Very (very!) mucky but solvent spray followed by detergent bath did make headway.

Stubaxle rear- lower O ring for Dust shield location.

Some headway with cleaning the part

Unfortunately cleaning revealed that at least one of these axles had a problem. Obviously they are not new parts so some signs of use are likely. However the offside stub was badly scored and seems to have had a loose bearing at some point. I don't think it will be usable.

Taper section O/S stub axle badly scored.

Andy was very understanding about this, apologised for the quality of the part and sent a replacement.

I had wanted to use a bench press in order to remove the existing bearings- largey because I now own one! However I was defeated by trying to mount the stub axle securely. It's a very awkward shape and I couldn't get a clean, safe line for pressing. If anyone knows how to do that please let me know. Anyway I reverted to plan "B" which was to use a draw-bolt threaded through each bush in turn as I have done in the past. The usual approach here is to use a suitably sized socket to press the bush, but sockets are always rounded  at their ends and any size transitions are sloped. This means that a socket tends to either slip off the top of the bush, or expand it as its trying to push it out. Once the bush is pushed below the lip of its housing this is no longer a problem,  but it can make that initial push quite tricky- and its definitely problematic when refitting. To avoid this I made up the following two adapters that can slip inside the bush for positive location and have a 90 deg shoulder to press on the  bush. 

Press adapters as made; Large bush 23/26 mm, small bush 23/21 mm

They are sized to slip down inside the housing keeping everything straight as the bush is removed.

Press adapters fit into the relevant bushes- pictured after bush removal! 

These were assembled onto a draw bolt (M8 studding) again using appropriate sockets to pack the thing out. Obviously you need a larger socket on the bush-accepting side and a smaller one on the pressing side. The assembly is shown below- using the removed bush to indicate its position. My drawer bolts are M8 studding but I'm using the roller bearing/thrust washer assemblies from a Draper press and pull kit which can be bought as spares.

Positioning the assembly really depends on where the sockets will locate firmly. I found that the large bush was best pressed inwards, and there isn't enough room for a really deep socket to be fitted there. This meant that the last few mm had to be tapped out with a hammer and drift on the push adapter, but luckily at that stage the bushes were pretty loose and came out easily. The smaller bush could be removed by pressing it outwards and there is enough room for a deep socket in that position. The draw bolt and adapter in use is shown below. 

Using a draw bolt to remove the bushes

This system worked really well and removed all bushes in pretty short order. 

I cleaned up the rest of the parts, one point of note is that one of the dust shields turned out to be partially home made. It will need some repair but seems to be functional. However, I will use a bona fide part for the rebuild if I can get one. I treated both stubs with metalmorphosis and then sprayed them black- I also treated the spare hub I had obtained- taping over all threads and holes- as well as any mating surfaces that shouldn't get paint on them

Both stubs and a hub repainted.

I bought a partial king-pin kit from Ebay- I needed to chase up various other bolts and seals but managed to assemble a complete set for both sides, with new trunnions and bolts top and bottom for rather less than the cost of a new kit. I will use the adapters to fit the new bushes too, but I may need to make an additional piece for the other end of the bush so as to ensure any pressing forces are exerted in a straight line and don't  let the bushes bulge outwards too much as they are inserted.

Insertion press kit as made

I made the kit as above where both adapters will slip easily into the bush- they need to be smaller in diameter than the kingpin as you don't want to get them caught up should the bush bulge inwards during fitting (as it probably will). The larger diameters were made to slip inside the housing smoothly so that they will hold the bolt central in the socket as the bush is pulled home. One adapter is pressed by a socket whilst the other is free to slide along the draw bolt. I used a short length of rubber tubing to hold it against the bush and let it slip along the bolt as the bush moves into place. Sorry to make heavy weather of this but I  hope the diagram below helps!

The adapters were both made to the same dimensions in each bush- if you get 26 and 23mm silver steel the the larger dimensions need pretty much no modification so for the larger bush adapter dimensions* A and B are 26 and 23.5mm, whilst for the smaller bush they are 23 and 20.5mm. Length isn't critical as long as the combined lengths of the narrower sections is less than the length of the bush!
*These are appx I will measure properly and amend asap

With these adapters I still needed sockets to press on both ends- a large one to sit on the outside of the housing and a smaller one that could be pressed in with the other end.  This meant that both bushes were best pressed in from the middle of the housing in an outwards direction since the outer surfaces are flat and smooth and the socket fits well there. When making the adapters, its really important to get a sharp 90 deg step on the pressing ridge, any chamfer here just bells out the end of the bush and it will not fit in like that.  I found these worked well. Using both press adapters the pull bolt is kept centred in the hole and the bushes press in easily.

New bush- oil grooves on one half only and no open ends.

 When fitting a new bush the manual states that the open ends of the grease channels should face towards the stub axle- I suppose to ensure that old used and excess grease is pushed up into the dust tubes where it might still do some good (?). The grease grooves in my new bushes had no open ends and  were only present on one half vertically- as in pic above, the grooves stopped half way down and before the top of the bush. Luckily the instructions also say that the split in the bush should face forwards (i.e. away from the stub axle and towards the wheel). This positions the grooves towards the dust shield side.

Positioning bosh, split faces outwards and grease hole in bush is in line with the nipple hole in the axle

Pressing in the new bush using the adapters

nearly home

in position, bush sticks up inside the axle but is flush with the recess on the other side.

The bushes are pressed in flush with the external surfaces of the housings and protrude a little internally. The remaining bushes were fitted similarly and without problem- the most fiddly part was making sure that the sockets had a fine seating on the stub axle and in most cases it was actually easier to press the bush home from the inside of the stub axle towards the outside as this gave a good seat for the large socket - see below...

Reaming is simple if you have the right tool and I got this two step reamer from MGB Hive- worked very well. As with any reamer- use lots of cutting oil and turn in one direction only. Also I have heard that reamers will cut again if you twist them out (clockwise obviously) so its probably best top pass them through once and then tap them back with a soft mallet.

Starting to ream

Always worrying- swarf coming out mid way.

However the job was very successful so I cleaned up the reconditioned stub axles and swapped all the grease nipples for new.


The top trunnions were a little corroded inside and the new bushes would probably not fit like that. The trunnion  needed careful dressing internally with a half-moon file to remove the worst of this and restore the double conical profile.

inside profile restored

There was also some damage to the top surfaces of both trunnions and kingpins where they were probably levered with a screwdriver in the past. This damage would obviously prevent the shims/thrust washer assemblage from sitting flat so this damage too was carefully filed flat.

Screwdrivering damage to trunnion/thrust washer mating face

Damage filed flat

I will treat the trunnions with Jenolite to stabilise any rust and hopefully prevent more before repainting them. I'll put the hubs and refitting all of this in a separate post.