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Gearbox - What's a spigot bearing ? - GazGriff
can someone please explain what the spigot bearing does and what effects it has when it has gone Thanks Gaz

Edited by Pugugly on 09/06/2009 at 21:12

Tags: technical issues

Gearbox - What's a spigot bearing ? - Peter.N.
A small bearing located in the flywheel in which the gearbox first motion shaft runs. If it fails, which is unlikely, the most likely effect would be clutch judder.
Gearbox - What's a spigot bearing ? - Number_Cruncher
The other possible effect of spigot bearing failure is clutch drag, i.e., an incomplete separation of engine and gearbox when the clutch is pressed, resulting in difficulty selecting a gear while stationary.

Where the gearbox input shaft is supported by two bearings inside the gearbox, if the input shaft is well sized, the spigot bearing doesn't really do much. Where this is not the case, on layshaft gearboxes, the spigot bearing is more important.
Gearbox - What's a spigot bearing ? - 659FBE
To add a little to the above, most German power units of this design (layshaft box) use a needle roller bearing rather than a bush in this position.

The needle roller is an inappropriate choice because it is very liable to be damaged when the gearbox is removed and refitted under "in vehicle" conditions of poor alignment and dirt.

Damage to this bearing following clutch replacement is fairly common, giving rise to clutch drag and further damage to the gearbox primary shaft. The heavier the gearbox, the more the likelihood of damage. Big manual M-Bs and BMWs are candidates, but the Audi/VW N-S gearbox is heavy as it contains the final drive. Fast fit centres generally don't score too well here.


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