Noise from transfer gear casing at idle

In reference to the 'ring nut' it's not a std type of nut. It was designed and engineered for accurate bearing pre-load, the thread tolerance is higher then a std nut and the face is ground to be perpendicular to the axis. Some use a separate locking tab washer while the ones Ferrari spec'd have a deformation ring. I seem to recall that SKF was behind ISO development. Updated locknut designs such as the SKF "KMTA" or Whittet-Higgins is what they are known by. The nut design that Ferrari uses is more accurate as the locking mechanism is part of the nut. I've toyed with the idea of using the newer KMT or KMK SKF nut but haven't done it yet. They have the advantage of being re-usable.

 

They have made and used identical nuts with a hex head. No reason in most cases why they could not have done it product wide but they chose to discontinue the few hex heads they used in favor of the ring nut pattern.

 

I suppose the nut could be made with just about any face but seeing as they are bearing lock nuts and fall into an ISO specification that was put into effect in 1971 (had to look it up) there was probably a bit of overlap or use what's on hand till we run out. The ring nut design is intentional so as to not use a std nut, the face of the ring nut is specific to the shaft and bearing it's applying pre-load to.

You should see the fastener requirements when doing military and aerospace projects ...

 

Ferraris use of ring nuts predates 1971 by a decade or more. The hex nuts in the same applications came later. Any decision by Ferrari had zero to do with ISO specs and many, if not most applications are not bearing preload related.

 

I found one of those on a 308 that had been bodged by some previous owner.
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Well that may be but I seriously doubt that nut is of Ferrari origin. A fix brought about by the prior maestros lack of the proper ring nut tool no doubt. At least he chose not to reinstall it with the chisel he removed it with.

The Italian fascination with ring nuts goes prewar. ISO started in 1947.

I suspect their traditional use has more to do with a tooling issue than any international standardization.

 

I don't understand why this becomes an argument, of course ring nuts existed prior to the ISO stds, all I'm saying is that once the ISO stds went into effect then most everybody would have used them to differentiate between hex nuts that lack proper design and ring nuts that are specifically designed for that application. If stds are going to be ignored then why have them? imagine non std wrench sizes, oh wait that did happen BSW, SAE introduced ATF sizing. (across the flats, vs bolt dia).

All the ring nuts used on the drop gears are to provide proper pre-load. The ring nuts on the main and lay-shafts do the same. The ring nut on the steering column, same again. Ring nuts on spindles etc.. all for proper bearing pre-load. Personally I've yet to see a ring nut used on a bolt for clamping load, if that has been done it'd be an odd thing for sure.

I have no idea why a hex nut would have been used at some point unless the supplier had ring nuts with a hex flange design from old stock still laying around. It's not a first for Ferrari to use what could be bought for less, or even fail to pay their suppliers and thus not get new stock.

I thought I'd simply share why ring nuts exist and why they are different. Obscure trivia really.