I have had to get a new gearbox shell for the Mk3 because the known bearing housing crack and an oval top mounting bolt bore. The new casing came from A-N via Norman White. I have just fitted the two shaft bearings and was preparing to install the camplate and quadrant. The casing came with the two spindle bushes pre-installed, so it appeared to be a straightforward assembly task.
However, I have found that the camplate spindle protrudes past the o-ring seal, causing noticeable spindle float. I had bought a shim out of curiosity, even though the old installation did not have one (nor did my previous Mk3), but it is an odd size, with a larger ID then the washer and OD of the spindle, and would cut into the seal.
I still have the old casing, so when I compared he two bushes, it was apparent that on the new casing, the bush is not pressed in as far as the original - this not only affects the protrusion of the spindle past the seal, but also the alignment of the camplate inside the gearbox.
I have not seen any reference to the bush in the manuals, other than the NVT manual stating it should be checked to ensure it is a ‘good fit’ in the casing. Is anyone aware whether there are fitting dimensions for the bush to dictate how far into the casing it should be set? If not, I will likely heat the casing and drift the bush further in until it matches the old casing dimension. If I did not still have the old casing, it would be guesswork, ensuring that the o-ring was still slightly proud of the casing.
If in doubt replicate the old part except for where its worn or broken, which is why I have a collection of worn out parts either to eventually fix or to check new parts against. The bush in the old position certainly could not contribute to the crack between the bearing or the wallowed out mounting hole so push the bush in.