Gear wheels technology.

[MIG Wielder]

When I were a lad, a few years ago, as part of the mechanical engineering course I remember being told that a new gear wheel should never be run against an old one.But I never asked why.
So ( as an example ) if you replace a gearbox input shaft you then have to replace the layshaft gear cluster, which means then changing all the gears. I don't thing gearbox recon; places do this do they ?
Or did I dream this ?
Thanks,
Tony.

[SprintMWU773V]

I think it can cause problems as the wear will be different. It's a bit like swapping half shafts from side to side, you shouldn't really do it.

[Carledo]

When I were a lad, a few years ago, as part of the mechanical engineering course I remember being told that a new gear wheel should never be run against an old one.But I never asked why.
So ( as an example ) if you replace a gearbox input shaft you then have to replace the layshaft gear cluster, which means then changing all the gears. I don't thing gearbox recon; places do this do they ?
Or did I dream this ?
Thanks,
Tony.

No you didn't dream it - but it IS a pipe dream! I don't build gearboxes any more but back in my GT6 days I did plenty! And mixed new and old gears (and often old gears from different sources) with total abandon and no discernible ill effects.
When I was an apprentice we rebuilt gearboxes with only partial new parts all the time and that was a Triumph franchise! And some of the warranty repair stories would make you hair curl!
Back in the bad old days, when manufacturing tolerances were wider, it may have been more of a problem and certainly what you (and I) were taught is "best practice" but in the real world it just doesn't happen, much too expensive!

Steve

[Jon Tilson]

Many is the Triumph main shaft gear set that's now with its 3rd or more layshaft...

People will keep bump starting cars in reverse....

What on earth did these folks think oil was for?

Jonners