Z3 facelift steering column / wheel spline changes

A

argy

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Hope someone can help please....

I designed a shortened steering wheel boss for my Oct 2000 Z3 which is enjoying a new life as a replica Ferrari 250 California. I designed the boss around the splined end of a 1998 steering wheel column, I have the final 50mm of a 1998 steering column and was able to successfully insert my new boss comfortably onto this splined end. The 1998 column is a 66 spline connection.

Having successfully tested the boss on the 50mm stub I was disappointed to find that when it came to installing the boss on my facelift steering column it wouldn't fit, at least not without a great deal of effort followed by an industrial grade puller to get it back off again. I have since heard from someone else that there are different versions of the steering wheel splined end so I'm wondering...

Does anyone know the specification of the splines on the facelift Z3 please?

It's clearly a larger outer diameter, but not by much. I believe that both are 66 splines but the spec for the outer diameter and possibly the inner diameter / depth of spline are sufficiently different to preclude a simple steering wheel (or boss) a direct swap.

Any input will be gratefully received.
 
Mine is a facelift and the spline diameter is 22mm. I was sold a boss that was listed to fit the facelift but the spline diameter was 18mm, I managed to get the correct one and adapt it to fit my 340mm Raid Air Bag wheel.
 
Thanks David,

That's interesting. I measured the outer diameter of the 50mm long pre-facelift steering column stub at 21.4mm. My facelift car was 100 miles away so I couldn't measure it. I now have my car back and I'll have to remove the forced-on boss so that I can measure the outside diameter of the steering column to see what the difference is.

Measuring the outside diameter of the steering column is much easier and more reliable than measuring the corresponding diameter from the boss because the splines get in the way.

I think I'll have to create a tapered tube tool to get an accurate measurement of the inside diameter from the boss so that I can then calculate the spline depth.

Fortunately I have a commercial boss with the correct splines which I should be able to use to measure the inside diameter. I'll have to hope that the spline shape hasn't changed significantly.

The 18mm that you mentioned is a much bigger difference than I believe is in play in my case I think I'm looking at fractions of a millimeter. I wonder which car your 18mm boss was actually intended for?

Where did you get your facelift boss? Mine came from car builder solutions and it fits my facelift column but it's about 25mm longer than required for my replica.

It would be nice to find a pair of toleranced engineering drawings for both versions, much better than measuring stuff....

Cheers
 
I am pretty sure this is the one I fitted https://www.ebay.co.uk/itm/204549820332 . Please bear in mind the diameters I quoted were Man measured with a tape measure and are approximate. My thought is that the pre facelift boss has smaller diameter spines and different clock spring mounting to the post facelift.
 
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