I’ve been in the garage and “think” I know what’s going on with the “clonk” or “click”..
2018 4/4 with 3,500 miles. Sat on its wheels. Wife rocks the steering wheel while I lie under the front with hand on the rack’s central L shaped bracket … the one the attached to the front of the rack’s central tube and which holds the inner tie rod bearings.
Very slight but tiny vertical movement just discernible at the L shaped bracket. Not really visible but just “feelable”.
I think this is a feature of the Morgan’s rack design where the tie rods come off the L shaped bracket that is bolted to the front side of the rack’s toothed rod. There has to be a very slight running clearance (not wear) between the rack teeth and it’s pinion otherwise it would be stiff. Also it will be a feature of the pinion teeth (normally) being helical and the way they mesh with the rack’s straight teeth. So, the toothed rack rod may have a tiny bit of rotation possible wrt the pinion. The tie rods are unlikely to be absolutely horizontal all the time. Mine, sat in the garage today, both had a very slight but discernible upwards inclination. On turning the steering wheel with the tyres on the ground the longitudinal force along the slightly inclined tie rods will result in a resolved vector component in the vertical. So, turning the steering wheel will result in small resolved vertical forces on the L shaped bracket. This could perhaps move the rack bar within the very small range permitted by the running clearance between the pinion teeth and those of the rack’s toothed bar.
If the car is off the ground and the wheels free to turn, the forces would be diminishing small even though the tie rod angle may be greater. With the car on the ground my bet is that if you load up the front suspension to increase the tie rod angle (heavier engined Morgans) the “click” would be more noticeable.
I think this effect would not be seen with a normal rack where the tierods come straight off the rack ends as the vertically resolved force would not be applied in a way that would rotate the rack’s toothed bar.
Bit of schoolboy vector analysis there but does that sound logical or otherwise?
Basically no lost steering movement, unless rack and ball joints truly worn, and no reason to worry I think. I expect they will all do it a a consequence of the rack’s design.
HJF... Well thought through.. there is nothing like a good mechanical puzzle.. I would add another consideration.. Looking at the Quaife racks GA drawing. The rack shaft is restrained at its furthest end ( depending on LH or RH version ) by a steel bush in the rack housing body to stop movement at that end of the inner rack rod. On the racks opposite end by the pinion, the movement between helical and straight cut gear is restrained by the racks preload adjuster to ensure correct preload mesh of the gears ( as per DaveW's photos), so in theory, the inner rack shaft should be able to resist vertical movement. However, the inner rack rod could still have a tendency to try to rotate slightly as the helical gear of the pinion engages with the gear of the inner rack. This would be restrained by the slotted inner spacer located between inner rack rod and the outer support tube/ L bracket bolts as the through bolts move back and forth along the rack body guide slot..
I note two points with this.. A: With the earlier Jack Knight rack design ( very similar to the Quaife redesign) GoMog hints that these spacers wear and B: The later Quaife redesigned rack has the outer section ( to which the gaiters attach) , named as the " support tube" .. Maybe the clue to this is the name of this part.. I suspect Quaife redesigned the original JK rack version to help reduce wear in the sliding slot area by allowing an outer sliding component to take some of the load as the load changes by track rod orientation.?.
Its possible that a combination of slight wear in the sliding spacers and/or variations of build tolerance produce more or less clearance in the slot area and the clearance between support tube and main body.. This mean that in some cars its a Click and in others a Clonk...depending on the load of the track rods to the L bracket..
When I place my hand on our cars outer support tube/L bracket I can feel a fair amount of movement and by placing a slight load on this area with my hand I can stop the Clonk..... but as said earlier the car has absolutely zero play at the steering wheel...
