Rear Axle Keyway Konfusion

[Iamscotticus]

I suppose, those who don't know better, would assume that Marina axles and Ital axles were the same.

But when they are put into the kit cars like Caterham did in the 80s and 90s, we 7ers are more particular.
They put them on the race tracks and beat the snot out of them. Then we have to fix them. This is where we learn the differences in axles, and why we need to know.

I am not planning on racing my Caterham with Ital axle, so Caterham claims that is an 3.64 Ital axle in the build manual, but I will be upgrading the axle to a high spec with LSD and upgraded half shafts, etc. Just to have the best bullet proof axle possible, without going to other, heavier options.

So, here is what I need to know... Do I have a Marina or Ital axle? All I can tell you is the hub key way is 3/16". I thought this was only a Marina thing. So I thought I have a pre 78 Marina. However, I am reading that the earlier 1.3 Itals were not built as stoutly, and had collapsing pinion spacers, and who knows what else? 3/16" hub keys?

Therefore questions arise I need to know like, if I have a collapsing pinion spacer, will a non-collapsing spacer from another Stanpart diff fit in?

@kilroy?
@SteveGreen thanks for the axle technical article, I forgot where I found it.

[MarinaCoupe]

I’ve never heard of genuine Ital half shaft/hubs with 3/16” keyway. Let me check the factory parts manual and get back to you.

Also if you are stripping the axle anyway, why not just check whether the diff has collapsing pinion spacers or not?

I think the thing is that whatever the axle had when it came out of the Caterham factory, previous owners may have subbed in other Marina/Ital parts, when say a half shaft broke. I’ve seen axles with a mix of one 3/16” keyway and one 1/4” keyway.

[MarinaCoupe]

Hi right-oh, there are no differences between the Ital 1.3/1.7/2.0 halfshafts and hubs, they are all 1/4" key-way. The standard differential pinion uses shims not collapsing pinion spacers. I think that its most likely that a previous owner broke a halfshaft and went down to the local scrap yard and stripped a halfshaft and hub of a scrapped Marina not knowing that there were any differences in dimensions. - in the 1980s & 1990s the yards were full of them. Have you checked the hub and halfshaft on the other side?

The Ital 1.7 (and Marina 1.8 & 1.7) all shared a 3.63:1 differential.

I have attached images of the relevant pages from the Ital parts manual.

[Iamscotticus]

Hi Chris.
I haven't torn down the diff to see what is in there. I am going on advice written in other forums about it.
But I can yell you that in the 80s, Caterham supplied kits with new I/M axles, up until they ran out and the DeDion Ford Sierra became standard. When the inexpensive Grads and Classic kits were introduced in the b90s, the I/M axles were reconditioned and cobbled together from parts as they were all torn down and rebuilt. I read of the fitter having to interchange I/M hubs when hubs wouldn't match. So, who knows what else may have been done. I know this, as it is stated in the Grahm Skykes paper on I/M axles, 1/4 key hubs were known to be put on 3/16 key shafts and shear. And sometimes the outter bearing was spot welded to the shaft. Horrible.
I know I have 3/16 keys on mine because I looked.
Thank you for the parts diagrams. I have two old 1971 BL Marina paper service manuals but the parts lists are not as detailed as yours.
Are yours available to down load?
Scott

[MarinaCoupe]

Hi Scott

That sounds like a bit of a lash up by Caterham. Something to be aware of although it may have been covered in Caterham documentation. When the Marina changed from the 3/16” keyway to 1/4” keyway in 1978, the also increased the diameter of the hub very slightly at the point where the outer oil seal fitted. This necessitated a change to the outer oil seal, but not the inner seal. Therefore you need the correct kit when changing the seals and bearings. Fitting the later kit to an axle with early 3/16” hubs will over time lead to a leak of axle oil into the drum brake area.

The 3/16” hub kit is GHK 1007
The 1/4” hub kit is GHK 1030

Both available from the usual suspects (Rimmer Bros etc.)

If you click on the images in my earlier post, they should open on their own, allowing you to either print them at A4 or save to a folder.