1993 348 Inner Axle Bolt

My thought is you need the same unthreaded bolt shoulder. Try bell metric or McMastercarr. I ordered factory studs for my engine when I rebuilt it and the factory part number parts were the wrong length. More often than not actually. I used bell metric.

 

First, you are measuring the bolt lengths incorrectly - the measurement should exclude the bolt head. It seems that your car has same driveshaft bolts as used on GTB, GTS and Spider which is p/n 139899, M10 x 1.25, 53 mm long (from under the bolt head to the end). Maranello appear to have these bolts (their supersession 223916) in stock - Ferrari part 223916 - Driveshaft Bolt M10 x 1.25 x 53 | Maranello Classic Parts (ferrariparts.co.uk).

I attach the parts catalogue for GTB, GTS and Spider.

 

Original bolt 139899 (M10 x 1.25, 53 mm long) has "allen" head (see the diagram in the file I attached or at Maranello), same as what you have shown on the picture above. The file I attached is searchable so you can search for 139899 (it is on page 146). As this bolt appears to be NLA, Maranello and Ricambi are offering 223916 in supersession. All you need is a different tool bit. The head on 223916 is much better for higher torques, it will not be easily buggered.

 

What type of head is that? I've never seen that before.

 

I think you are getting the nomenclature a little backwards:

A "normal" bolt with 6 flats on it is called a Hex Head.

What you are describing is an Cap Head Bolt or an Allen Head Bolt. I have sometimes seen these are referred to as an "Internal Hex" bolt as well.


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223916 looks like E-Torx. So much better than an allen head and much less easy to strip.

 

Its a plain old 12 point. But it is better.

 

I replaced mine with the 12 point version. Can send you some of my old ones if you like.

 

Bolt 223916 is just $3 at Ricambi, £2 at Maranello. Not too expensive to replace all of them.

 

LOL - silly me - it didn't even dawn on me. So a regular wrench or socket will spin that thing? oh my...I need a vacation.

 

First on the fourth page.