Hi
I am currently in the process of rebuilding a 1928 axle with the early type of diff carrier. I was advised to get the diff carrier crack tested as the bosses on the side can harbour a crack at the obvious stress concentration where they join the bulk of the carrier.
Magnetic particle crack testing this evening has revealed one side has a short (4mm) crack where the boss joins on, exactly where a crack might be expected to start. Does anyone have experience of finding cracks in diff carriers, please? Does a 4mm crack suggest (as I suspect) that I would be best finding another (uncracked) diff carrier?
Regards
Colin

Colin,
In most cases any crack is bad news. The bottom of the crack results in a region of very high stress and it will most likely propagate unless the area of high stress can be eliminated(usually done by drilling a hole at the end of the crack in a plate). In this case you cannot do that. If the crack is showing up as 4mm at the surface it is likely that it is at least 1mm deep.

By far the best bet is to get another un-cracked carrier. I haven't got any of this type on the shelf so I can't help out. I am sure the cherished suppliers will be able to help you out.

Tom

Location: Guildford

hi colin,

the crack will break. just like it does on the cranks. (eventually)

but it is like a length of string.

if you put it back, in time you will find out how long that piece of string is.

your choice.

tony

Hi
If I go for a later symmetrical diff carrier, are the differential gears the same, please?
Regards
Colin

I think the differential gears are the same but the crown wheel isn't. The later carrier is much stronger.

Location: Isle of Skye

Hi
Thanks Jim - yes I think the carrier was kept the same to the end of production (apart from the alterations to half shaft diameter in August 31 and July 38) so I suppose it must have been strong enough to cope with the much heavier Ruby.
Regards
Colin

Four Austins went to Normandy three weeks ago and one broke a halfshaft. When we split the diff. the nearside boss on the late type carrier was completely broken away from the rest of the carrier. He got home ok though!
Steve

Location: Sunny Somerset

For the record, it was the boss on the offside that had sheared and it appeared that a great many miles had been covered in this state. This is suggested as it had been noted that for some time there had been an horrible roughness in the transmission when reversing but only a bit of a whine in normal driving.
It can be argued that in forward motion the thrust from the crown wheel is directed on to the nearside diff bearing and this had saved the day. The converse applies in reverse and hence all the roughnes. The bronze bush inside the sheared boss remained intact and had carried the load though the halfshaft! All part of the resilience of the Austin Seven!!

Ron

Location: Thornbury S Glos