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Easter Run
#1
was a fantastic sunny day so took the Chummy for a run. Sadly 20mms from home she broke a half shaft.

Question- as I’m going to have to find a replacement would it be better to replace both now with new ones?

Bryan
Top off the north island nz


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#2
All depends upon your budget. Its a classic failure when it snaps at the end of the keyway. Once you have stripped the axle down, you could crack test the other half shaft and decide then, adding time that the car will be off the road, or go for two new ones.
BobH
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#3
Looking at the photo of the broken off end it seems to me that the cause of the failure may have been a loose taper.  Probably a good number of Austin Sevens are rattling around on their key ways and I wonder if the cause of half shaft failure is as well known as perhaps it should be.  

I remember reading somewhere that the key way is only there to allow the hub nut to be tightened; the working load is taken by the taper which needs to be fully mated and tight.

If my memory serves me right, half shafts should be replaced in pairs as a mater of course.
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#4
Thanks Ray,
I suspect it was loose hub as well. Interesting there was 2 washes behind the castle nut.
Took the near side hub off last night. The hub nut wasn’t tight and the puller had no problem removing the outer hub, the taper is also looks to be in a bad way.


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#5
I would look to replace both of those Bryan. You probably know that short shafts come in two sizes, you need to measure your existing ones (⌀) and replace with same.

I always fit new diff lip seals in place of the felt ones.
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#6
Finally had time to get the diff out to measure  the half shaft size. Sadly the pinion doesn’t look so good Sad


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#7
HI Bryan,
It might just be the light but it looks like the pinion has been to deeply meshed and has been running on the base what does the C/W look like,
You will also need to look at the Hub no point fitting new axels on warn hubs.
Colin
Tinopai NZ
PS When fitting new keys check that you have clearance on the top of key
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#8
Is the castellated nut and split pin part of the problem? If there were no split pin (as I think Bob Culver has recommended) nipping up the nut periodically would be an easier and more obvious thing to do as part of regular maintenance.

A question for the experts: If the taper is lapped in with fine paste and the nut tightened to approx 150 lbs/ft, is failure over time still inevitable, or are these failures due to incorrect assembly in the first place?
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#9
I would agree Colin, and unfortunately for Bryan not so easy to find a replacement for screw in torque tube diff's either
Black Art Enthusiast
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#10
Hi Colin R, the crown wheel looks ok at first glance (no chipped teeth).
Was looking at get new half shafts and hubs as the existing weren’t on the the tapper very tight and already had washes under he crown nut. (Wasn’t done by me).
Colin W, the nuts weren’t very tight and had split pins.

My question is, is the pinion useable and if not dose anyone in nz have a spare for a screw in torque tube and do you have to replace both the crown wheel and pinion together as a pair?

( sorry if this is a silly question but never done a diff before)
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