There have been several threads on the MGOC forum in recent years discussing repairs to these columns in the shape of bushes and shear pins, each with their own useful bits of info and pictures, so I thought I'd pull them together. Bushes first, as this is likely to be done for its own sake, as well as part of a shear pin repair.
Ben Colomb posted the following pictures and descriptions. Old and new bushes - upper (MGP1050P) on the right, lower (MPB1002) on the left both for the intermediate collapsible column:
The old and new lower bushes are quite different. This MGB Register post says that the old bush had an ID of 25.6mm and an OD 33.3mm, whereas the new MPB1002 is 26.5mm 34.5mm respectively, so is loose on the shaft as well as being too big for the outer tube. The old bush is also double-skinned whereas the new is solid, and has a choice of three notches to engage with a projection inside the outer tube to prevent it from rotating, which the new doesn't. Robin Goujah says his old one was the same i.e. double-skinned etc., but had been cut along its length. Possibly an earlier replacement using the original bush, fitted from the UJ end without dismantling the column, as indicated below. He said his new one was also about 1mm bigger than the old in both ID and OD:
Brendan Hussey sent me these dimensions - old bush:
Ben describes getting the new bush onto the shaft as 'the difficult bit' - "The lower bush is more of a problem as it has to be eased over one of the joints in the steering column and then pushed into the lower part of the column. This can be quite time consuming. The first pic shows the bush being eased over the joint, I used a heat gun to warm up the bush so as to expand it slightly to help ease it over.":
However I suspect the 'joint' is in fact the socket for the steering lock deadbolt, and in saying "the bush being eased over the joint" the implication is that the arrow refers to the bush being pushed from right to left. But looking at the bigger picture the bush must have been pushed down from the steering wheel end i.e. from left to right over the shaft, so the arrow refers to the direction the shaft is being pushed through the bush. If the steering is locked when the column is removed from the car it will need to be unlocked to withdraw the lock deadbolt from the shaft socket in order to withdraw the shaft from the tube.
Ben also writes "Not sure if it's relevant but my column had a little dint pressed into it which lined up with a notch pre-drilled into the bush...". I've not seen that drilling in any other pictures of the new bush, but the projection inside the column tube seems to be standard:
"To get the bush into the column I drilled a hole in some wood I had around, smaller than the diameter of the bush, passed the column through it and drifted the bush in. (This) also shows what I think is the collapsible part which someone has welded together, for better or for worse". Welding the two halves is one way of dealing with a collapsed shaft!:
So Ben got his bush into the outer, and I'm wondering if forcing a 35.4mm bush into a 33.3mm tube compressed it onto the shaft taking up the 1mm ID clearance.
Robin fitted the bush into the column outer slightly differently to Ben but the effect is the same. With the shaft gripped by the jaws of a vice, and the bush against the side of the jaws, using a block of wood as a buffer and a 2lb lump hammer hit the other end of the tube. With both bush and column tube greased, and turning the tube between hits, the bush slipped into place. As the shaft has to be partially withdrawn from the bottom of the tube and the bush to do this, make sure the bush will pass over the repaired shear pins. Also make sure the column lock is unlocked, or the shaft has been withdrawn far enough, to prevent the lock deadbolt hitting the end of the socket on the shaft:
As the bush ends up near to the UJ splines, Ben must have pushed the collapsible part of the shaft through the bush as well as the lock socket. I would have thought the bush would have been fitted from the bottom of the shaft, over the UJ splines ... but as this from Robin Guojah shows there are three fat welds and a flange where the solid splined shaft has been welded into the collapsible tube, so it's not possible:
Justin Ravenhill posted this on yet another thread asking how far the lower bush was pushed into the column outer:
However in practice there is several inches of lower shaft exposed once everything is back together. This shaft is probably protruding a little more than when fully installed, as shown by the witness mark on the shaft - the shiny portion, which would normally be inside the bush. To push the shaft back through the tube to this point the lock will have to be disengaged otherwise the shaft socket will not get past the lock deadbolt:
At least there is on the 4-cylinder intermediate column. The V8 and RB 4-cylinder full energy-absorbing column has the inner protruding much less as shown on the left here, and seems to be the same diameter all the way up after the splines (right), which should make that bush much simpler to fit:
See also this from the V8 Register.
Ben Colomb continues - "The top bush is very simple, just a straight push in job" (4-cylinder CB only):
As it seems to be only the top bush that is tested on the MOT, and that is much easier to replace - perhaps only removing the steering wheel (and cancelling cam) and not the whole column from the car with the realignment for the UJ that then needs, maybe the lower bush is best left alone! Robin says after completing the job the shaft is quite tight to turn with the new bushes. Some of that will be from the upper bush, but forcing the bush into the outer seems to have compressed it onto the shaft to take up that 1mm gap, so removing a source of noise at that end as well as unwanted movement at the top.
Shear pins: Robin Goujah's sliding joint with plastic pins in place, but worn and allowing play. There is an additional short roll-pin between the two pegs, probably the result of a previous repair attempt:
Graham Barker's remains of the injection-moulded plastic, which goes all the way round a 'waisted' section of the inner shaft as well into the holes in the outer:
That looks to be the same as in the later full energy-absorbing columns as used on the V8 and RB 4-cylinder cars. Quite a bit more work is needed to remove the shaft and upper bearing from the outer in these, so I chose to work through the mesh:
A picture of a dismantled sliding joint from Gerry Masterman, without Robin's roll-pin. However being from America this is probably not the same column as either the intermediate or late UK/RHD shafts. The shape of the injection-moulded part looks similar. Note the inner shaft has been drilled through:
Various methods have been employed to reconnect the two halves of the collapsible joint. A popular one is a hot glue gun, which needs the whole area to be heated up to allow the glue to flow all round the joint and out the other side as originally. Others have used split-pins (which could prevent the lower bush from being slid over them) or screws both of which need the inner shaft to be drilled. On my full energy-absorbing column I opted to leave the nylon in place on the inner shaft, just removing the 'pegs' from the outer. Then drilled a small hole right through to insert a pop-rivet pin, and dribbled Araldite in the 'peg' holes:
Robin drilled right through the remaining inner and out the other side of the upper column and inserted a 2mm roll pin all the way through. No guarantees but he suspects that it will shear the roll pin if there's an impact. Followed instructions for the hot glue gun, and tapped the new roll pin through both halves of the collapsible section:
Whatever method you use to fit the bush into the shaft, to get the shaft fully back into the column make sure the collapsible section can be passed through the fitted bush, and that the column lock is disengaged. Once inserted remove the key to lock the column and it will keep the shaft in position.
When refitting the column as well as having to realign for the column UJ, the outer tube is able to move in its brackets. The column inner position is set by the UJ and the rack, so the column outer can be slid through its brackets, to correctly align the cowl and the horn brush to the steering wheel. The cancelling cam can be slid to align with the indicator switch, which is correct when the cam is facing the switch with the wheel in the straight-ahead position,