Christian, maybe it isn't the car. Maybe the problem is that you have been spending too much time in the gym!
Maybe the issue is with the steering gear box. I think there's a torsion type of spring that deflects when you turn the wheel and the more the spring deflects the more hydraulic assist there is. Maybe the spring is damaged or has weakend from age.
I've never done any work on these steering boxes but the mopar stuff I used to work on had just such a wave spring. A deflectable flat wide washer that controlled the amount of effort required to turn the steering wheel. We had a special thicker washer that was used in police cars and the TA Challenger and AAR Cuda models. We replaced every stock spring with the "high effort" type. It required more input torque to turn the wheel and conversely gave more feedback from the steering system. If these steering boxes have such a part maybe the wrong one was substituted or as mentioned damaged. The difference in the two washers was less than .010" in thickness on the Chrysler steering washer. Maybe worth inspecting, that is if Ferrari used such a part to tune the required input torque.
Mitch, the problem is that no shop knows what the fix is so the car goes in, steering box is removed (including left front suspension so the car becomes immobile) and everyone scratches their head at $shoprate. My guess is that its $1k just to R&R the steering box. What i'm hoping for is that someone has seen the inside of the box and can describe whats going on. Jim and Dave are definitely on to something I hadnt heard from any Ferrari tech previously. My next step may be to drain the system and remove the top cover of the box to see what I can see. And I'm definitely going to stop working out, John.
Taking the top off=Pandora box! LOL I can just picture springs and ball bearings falling out and onto the floor then rolling down the floor drain. Proceed with caution. I've never taken one apart, just read and looked at pictures.
I took the steering box apart to replace leaking seals on my '68 Cadillac. I won't EVER do one again. Full stop. Never.
I only used two shops in the 50 years I was in business. Straight Line Steering, San Jose was THE best. Quick and reasonable. The other far more expensive X2 and not always able to fix
Christian, Isn't this a ZF part ? I know Porsche and BMW used ZF-boxes in the 70's. Have you tried searching the ZF number on your box ? I wouldn't be surpriced if it's has links to BMW. If so,there should be plenty of websites with parts and "how-to" information. Maybe not relevant,as it's for a 365 GTC,but might contain good info : Tom Yang's Ferrari Restoration Best of luck
It is a ZF box but only shared with the C4 and an odd Lambo, both of which are very limited production. I think the price of spare units is very high because they can be fit into a Daytona. I have a good work space, I'm patient and will dig into it soon.
I've found a source for a used steering box. Can one of y'all with RHD Take a close look at the steering box in your car and confirm the part number? Russell, I think your car is most similar to mine for age. I will disassemble both boxes and try to see what's gone wrong with mine. Thanks in advance.
I would carefully check the torsion springs on the input shaft. Don't know about this specific box but some have thin leaf style springs that are paired. They have a curve in them for the preset tension and should be installed faced to the other. You have to squeeze them together to slide them in their slot. If those springs have been incorrectly mounted you have the wrong or no preset torsion load on your spool valve and open as soon as there is a movement. It is those springs that give you the desired needed effort. Could the ball you found been a indexing detend ball to center the spool? Take pictures if you can. From what you describe I think your problem is in the spool valve preset tension.
Christian this is a different model of what I've ever seen but I will try to explain the fonctionning and you should be able to figure it out. Part 40 and 130 are what look like the hydraulic valve part of the box. Your hydraulic hoses must be connecting into part 130 if my understanding of the drawing is correct. I think part 45 to 48 and 451 might be the springs assembly I'm talking about. What you need to understand and check is the following. Part 40 has the input shaft on one side and the worm on the other side. In the box I've worked the input and the worm are two different parts. They are joined together with a play from left to right. This play is the valve opening movement. This play has to be centered in the middle with a spring load. When you turn the steering to one side it has to beat the spring pressure before moving to the stop. This is the hard feel you have in the steering. Only after beating the spring it start to open the hydraulic passage to the side you turned and give you the hydraulic assist. When you stop turning the steering the spring recenter the spool and stop hydraulic pressure to the box and open the flow in a open loop with no pressure. Same for the other side. If for some reason there is no spring load on the spool it open as soon as you turn the steering with no feel of load at all and like you said the steering almost turn by itself because there is no spring to return it back to center and keep the hydraulic passage open. If you have a left to right play on the input shaft that is easy to move by hand this is the culprit. BTW the loose ball bearing could be one of the recirculating ball that has fallen when it was taken apart. These balls are a bit of a tedious job to put back in place correctly. Sometimes mechanics think they are all in properly but one has passed over the passage and after a few turn of the steering it fall inside the box and limit the travel of the piston. I see this a lot with my students. Make sure you check all the guide pins or dowel are in their slot. Don't force anything if it doesn't close as it should. I hope this help!
Also, understand that the relief valve you opened and cleaned does not control the working pressure in the box but only the MAX pressure to which it should work. This valve usually open only when you reach the left or right stop of the box. The working pressure is determined by the force against the wheels and is lower than the relief pressure except if the movement of the wheels is opposed to a more than normal force.
