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BJ8 transmission mainshaft bearing force needed to install/remove


Obi Wan
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I'm rebuilding the BJ8 transmission.

I used a hammer to get the dry bearing into the dry mainshaft bearing housing/carrier. (I don't have a press). Very tight. Putting the dry bearing/housing on the dry mainshaft, it takes just a couple light tapes with a hammer. Yesterday I was able to pull the bearing off with my hands, no hammer tapping to get it off. (Everything is covered in 30w non detergent).

A Youtube video by Manus Karlsson, “Austin Healey Mainshaft Assembly” at timing mark 4.00 shows him hamming the bearing on the shaft.

My gearbox is loud and I'm finding metal filing on the magnet I installed. Could the issue be related to the bearing not being as tight on the shaft as the video shows?

If I put a new bearing on and it doesn’t take much force to put it on, is there anything I can do to the shaft where the bearing sits, to have it tight? Or do I need to buy a good used mainshaft or new mainshaft?

As always, thanks for your help.


Great Pumpkin
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Not to be a 'Debbie Downer' here, but it would be my advise that the mainshaft be taken to a (competent) machinist who could build up the diameter of the shaft (not just torch some material on it, rather "spray" it as crankshafts are built up) and turn it down to spec. A slight interference fit, no idea what the original diameter should be, but somebody here with a good shaft should be able to use micrometers and post it.
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