Reply to "Longchamp Steering Rack"

There are several threads about steering racks which all seem to share the view that the Cam Gears RHD rack on the early Longchamp is not rebuildable. Long before the days of digital cameras and forums like this I rebuilt the rack on my 75 longchamp (maybe 16 - 17 years ago).

The job could not be described as easy (that much I can remember), but it was not impossible. Unfortunately unless I pulled it out again I would have a lot of trouble remembering exactly what had to be done. I certainly recall being told they were a ZF unit, and studying workshop manuals in public libraries for a range of cars looking for ZF operating principles. Turned out it wasn't ZF after all and now I know what it is.

Eventually I just pulled the rack and dismantled it to figure out what was wrong.
I remember that the operating principle was one of the best I have ever seen, with boost being proportional to load - controlled by a small pilot valve which was fixed between the chassis and the rack. From memory the reaction forces on the rack admitted fluid through the pilot valve to actuate the piston. The movement would have been pretty small! So when you were parking the force was great, the rack reacted more, so you got more boost.

On a straight line open road you have little or no reactions, and hence no boost, its just like driving a non assisted rack and pinion (albeit with a clevo on the front wheels). Given this was 35 year ago technology, compared to its contemporaries it was astoundingly good.

One of the tricks with putting it back is the need to shim the pilot valve exactly to its central position, otherwise when you turn you get much more boost on one side than the other. I do remember having some trouble getting this right.

I think a steering specialist (used to old cars and not being asked to quote a firm price for the job) or a very competant self taught detomaso owner would be able to do the job, as long as the time off the road wasn't an issue. Seals and things would have come from an industrial suppliers, and may even have been just O rings, but I'm guessing. I know that back then I didn't have a vendor option.

If someone needs me to remember more I could always crawl under the car and have a look at it again.

Peter