There are many ways in which the Lightweight gearbox can wear. Don't worry if the components aren't perfect; these gearboxes are simply designed and will usually continue to function well, even when worn.

In the picture, a breather union (visible in the top-right corner) has been fitted to the gearbox casing . This is a modification for racing use, so it can be ignored here.

The layshaft bush is almost always worn oval. It may be so loose that it just falls out; assume you will need to replace this bush.

Check the large output bearing for signs of corrosion or roughness. If in doubt, it is a good idea to replace it. Note that it is a special part and is very expensive.

Check the output seal for signs of oil leakage.

Check the selector pivot shaft is secure. It can work loose and cause oil to leak from the end of the casing.

Check the two steel plugs are secure and oil tight. Drift them out if in any doubt.

Later gearboxes may have a hole for a pin to secure the layshaft bush. Check the pin for security or signs of oil leakage. Remove it if in doubt.