By Gordon Maltby
[Editor: The steering coupler is a sometimes neglected — but critical — component of the steering system. This article, reprinted from the 356 Registry magazine, Vol. 30, No. 2, explains what it does and what to watch out for!]
Every Porsche 356 is equipped with a rubber bushing in the steering column. Its purpose is to dampen vibrations through the steering wheel to your hands and allow a slight amount of flexiblity to the entire connection, since the steering box is anchored solidly to the top torsion bar tube.
The A/B Coupler — Sturdy and Reliable
356A and B cars used a simple rubber disc (a VW part) that has been reproduced in various forms over the years. The original idea was somewhat like a tire's construction, with rubber molded around woven fibers. Some of the replacements available over the years are just rubber, and some have more fiber than others, like the sorry sample Richard Miller sent (below at right). He says it was still in use in this condition, and of course, the owner had noticed a bit of play for a long time. At some time while driving, the steering wheel was pulled back just enough to truly separate the ends of the steering wheel and steering box shafts, and we can imagine things got really interesting at that point.
Since the steering coupler is under a cover, under a mat in the trunk, it's not something you'd be looking at on a weekly basis. But since you're changing your brake fluid every year (right?) you might as well spin the steering column and check for cracks while you fill the brake reservoir.
The flat rubber disc for the early cars through B models is pretty tough — as Vic Skirmants told me, "They look like they were made from the tread of an Afrika Corps truck." [Editor: but they can still wear out, as the photo provided by Ken Daugherty, shown below at left, of an original A coupler attests to. Middle photo is an unworn A/B coupler. Right photo is a disintegrating A coupler, perhaps an old aftermarket replacement.]
The C Coupler — Not So Much
No so with the C model coupler, however. Made of four triangular drilled aluminum pieces bonded together in molded rubber, they are well known for cracking over time. Replacements have been very expensive to unavailable for a long time, but both NLA and Zims, among others, offer alternative kits. Both use double discs, metal bushings and locking nuts, and supply new ground wires for the horn circuit.
This is not high-tech engineering or a difficult repair, so do not ignore warning signs of coupler aging or damage. When removing old bolts be prepared for the normal rust seizure, and use new castellated nuts with cotter pins or locking nuts. All six bolts, including the two that pinch the shafts at either side of the coupler, are meant to be locked. (Shown at left, the factory C coupler and its connecting components, including the rare 30mm steering wheel extension.)
If it happens that you are driving and somehow the coupler fails, be sure to push the steering wheel forward as hard as possible while steering. This will, hopefully, get you to the curb, but not intothe curb. Drive carefully.[Editor: many thanks to Gordon Maltby for his permission to republish the above article from the 356 Registry magazine, July/August 2006 issue. More information on the various aftermarket coupler kits from well known 356 vendors, and comments on coupler failure by experienced 356ers.]