Rear Axle Interchangeability

[Chris KC]

On page 165 of A7 companion, in "Notes from a series of lectures by J. French on building a 750 Formula car" there is a para which reads as follows:

"It is a long time since I saw any new spares for the 1930 "screw-in" torque tube axle; later pinions are too short and I don't think a wangle is possible here. You can, however, change the entire torque tube assembly for any of the later types, which process, in effect converts the axle to '31 type. This enables you to use any pinion which has the bearing retaining thread."

Can anyone suggest what the second sentence means exactly and how it would be accomplished? I can't fathom how a bolt-on tube would be fitted to a screw-in casing without a fair bit of butchery; and if it in fact refers back to the 23-29 axle type, the 'nose' on the banjo is shorter. Is it just a mis-transcription?

[Scarlet O'Hara]

Would it work if you changed the torque tube for a flange one along with it's appropriate diff casing (and crown wheel?) but retained all the other parts - differential gears, half shafts, axle tubes brakes etc? Sounds like it might be easier just to replace the whole axle.

[Stuart Giles]

I think that the bit Jack left out of that sentence was "along with a 31-32 diff case" there's no way you could fit the later torque tube to a screw in type centre section without a lot of welding and machining work.

[Chris KC]

Work, yes - but as you say, this more or less equates to throwing away the 1930 axle and replacing with 1931 type.

[Parazine]

What he meant here is that the whole torque tube plus banjo can be swapped for the later type. You can use the banjo/torque tube from the early LWB axle here as well, effectively converting a LWB type to a SWB type. The screw-in (SWB) axle used the same type of side tube with the crown adjusters as the later axle, however the adjusters themselves don't have an oil return thread in them.

[Chris KC]

I have no doubt that's feasible; and thanks to all for your thoughts. It seems a strange choice of phrasing though if that's what Jack intended - he was nothing if not eloquent. Moreover it doesn't seem terribly useful as dodges go. Sadly we can no longer ask him.

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What he meant here is that the whole torque tube plus banjo can be swapped for the later type. You can use the banjo/torque tube from the early LWB axle here as well, effectively converting a LWB type to a SWB type. The screw-in (SWB) axle used the same type of side tube with the crown adjusters as the later axle, however the adjusters themselves don't have an oil return thread in them.

On further reflection, Jack says ANY of the later types; you couldn't do this with a 'D'type banjo...

[Rogerfrench]

I think the first time this anomaly was noted was probably in 1952, when he first wrote the article. I can confirm that he did mean the entire assembly of torque tube and banjo from pre-32 D-type axles.

[Chris KC]

I think the first time this anomaly was noted was probably in 1952, when he first wrote the article. I can confirm that he did mean the entire assembly of torque tube and banjo from pre-32 D-type axles.

I wondered if you were reading, Roger! And it did cross my mind someone had probably queried it before! I know I'm slow on the uptake but that has to be a record...