I'm rebuilding my gearbox. Bearings, shafts, gears and consumables are all brand new from Andover Norton.
Everything appears to rotate as it should with the inner cover in place but without tightening the mainshaft nut or the nuts on the mounting studs. But tightening either of these locks up the mainshaft and sleeve gear.
I've successfully rebuilt a Commando gearbox before (albeit many years ago). What can be the issue here?
Do you know the gearbox…
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incorrect 2nd gear
Julian could you have been supplied with the wrong gears. Check the new gears with the old gears.According to the American service notes second gear was changed after s/n 306591. The difference is only one tooth ( old 24 T ) as against new ( 23 T ) on the lay shaft. They look the same but are not. I found this out the hard way. The rouge gear now has a ticket tied to it in my box of gearbox spares.
Check the number of teeth on the new 2nd gear compared with the old gear.
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2nd gear....
I understand the gears are supplied in pairs and MUST be kept as the pair. Nothing to do with better ratios but reducing noise for Manufacturers MOT!
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Thanks to all for their…
Thanks to all for their comments. I hope to revisit things today, and will reply in more detail then. For the time being I am reluctantly coming to the conclusion that one or both mainshaft bearings is not fully home.
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It was the layshaft/kickstart spindle bush 04.0146
Feeling discouraged, it took a while to summon up the enthusiasm to try again. But eventually it occurred to me that assembling with each shaft separately (and with/without gears) might help isolate the problem.
It only appeared with the layshaft with gears; close inspection of the relevant parts suggested intimate contact between the hub of the layshaft first gear (04.0115) and the bush in the kickstart spindle.
Application of a hammer and drift to the bush moved the latter about 1 mm (depth from face of spindle to face of bush increased from ≈ 11 mm to ≈ 12 mm).
All now seems good.
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Do you know the gearbox shell and cover to be good? Is it a lock-up as in it goes stiff, or as in it jams solid? All gears, including neutral? Have you shimmed anything? Are you using a gasket?
Might start to stiffen up if the bearings are not properly seated or a selector fork or shaft is bent.