J type O/D gearbox input shaft - acceptable play?

[sparky_spit]

I have a spare J Type O/D gearbox that was running for quite a while in my Spitfire some years ago. It was working fine but after after a bit of a general rebuild of the whole car it ended up with a newer box out of another car I'd bought and has been sitting under my bench ever since then, wrapped and greased/oiled. It all looks good and ready to go, but I wanted to get some opinions on how much up and down (and side to side as well I suppose) is normal. I don't remember it being a problem when it was being used, but would like an opinion on what amount of play is normal. Thanks in advance for any help with this.

Edited July 30, 2023 by sparky_spit

[Nick Jones]

New/fresh rebuild have very little play.

2-3mm radial play at the tip is perfectly acceptable IMO. 1/2” is not….

Also worth checking whether there’s any axial play as that tends to be an indicator of whether the input shaft bearing is tired. This should be minimal.

[glang]

The good news is that its very easy to get access to inspect and even replace the input tip bearing. At the same time, if it has one, you can also replace the input oil seal - something which, along with the output seal, is always worth doing as a minimum before installing an unknown gearbox...