Bump... does anybody know if this would work on an early 86? I have been scouring PET and don't see anything like a restrictor in the diagram, doughnut shaped or otherwise...

 

78-84
85-90
91-95

Hard to tell with the sticker there, but I don't see the restrictor on the 91-95.

 

Having first hand knowledge, the 85-90 shown above is actually the one that fits my GTS. I had my power steering hose rebuilt without the restrictor and I installed it yesterday. I drove it and there are no ill effects. The restrictor, at least for my MY, was likely for noise suppression.

 

So.... would it be possible to remove the restrictor in the existing hose and splice the 2 ends, or would the fact it's a high-pressure line make splicing it an impossibility?

 

I like my steering just the way it is and don't mind the heavy effort at low speed. I think I would rather save the expense for the gym. It will do more good for me.

 

I wouldnt splice, wont hold.

 

What heavy effort?

 

I am used to it, but when I jump in another car I can feel the difference. Also on the very rare instance I let someone drive, they complain about the heavy steering and then say wow when they start driving.

 

Haven't driven many 928's, but the "heavy steer effect" in my s4 is absolutely unnoticeable but in those situations:

1. Fastening seatbelt while you steer out of the parking ramp. Doesn't bother me much, really.

2. Heavy counter-steer situations. I usually keep both hands where they belong (old good quarter to three) which is the only way for me to control a drift. But at slow corners (more than 180º steer imput) I have to move them and I keep myself from playing with the gas at all. However, one eventually have to handle a sudden power oversteer, and I find my emergency reaction much slower than with my light steered cars, both unwinding and winding it back. Spinning completely is the easyest way to trash the car in my local circuit, and a small improvement in this area can save me big money!

3. Shifting at slow corners. I can live with it.

 

A few questions for the group. I 'd like to replace my rack with the later model version since I've got 9" wheels up front. My pump is whining so I will be replacing it also with a Griffiths High Output pump for 85 to 90 MY from 928 Spec. Will I need to change any other parts for the later model rack to work? Are there any parts needed that are not included with the rack and pump that I will need to buy? Is the Porsche dealer the only source for the later MY rebuilt Porsche rack referenced in Nicole's original post? Lastly, are there any other WYAIT items I should consider? The motor mounts were just replaced. I let my local shop do that but I'm planning to do the rack and pump myself. Thanks for any info you can provide. This forum has been an amazing asset for me since I brought my dream car home.

 

I have rebuilt two racks, and will do a third this weekend. There is only one kit of seals from Transtec, and I believe them to be the supplier for ZF rebuilds of any kind. Therefore I do not see where the "low friction" seals would be comming from.

Now pressure is a different thing, but nicole is speaking of specifically a different rack. Is it the fact that the "arbor" or "shaft pump" thing in the rack is designed with more leverage hydraulically speaking? Because seals are seals. The only thing I can think of is that the rack has the center shaft ID coated with something more slippery.

 

For most racks, the difference is in the spring in the spool valve, that little part that sits between the input shaft from the steering wheel, and the pibion gear itself that engages the rack. The amount of distortion that the spring allows is usually what determines the amount of assist that the hydraulics supply. Weaker spring, lots of assist. Taut spring, less assist. Most 'speed sensitive' PS setups depend on engine speed to vary the pressure to the rack by monitoring the pump pressure. Kind of like the rising-rate fuel pressure regulators, inverted. Not an issue for the 928 of course.

Brendan,

Could you take a few pics of the pinion assy, out to the input shaft? It should be pretty easy tospot the ports/grooves above and below, where the fluid channels around these parts.

Thanks!

 

Lifted from "How things work "The input from the steering shaft forms the inner part of a spool-valve assembly. It also connects to the top end of the torsion bar. The bottom of the torsion bar connects to the outer part of the spool valve. The torsion bar also turns the output of the steering gear, connecting to either the pinion gear...

As the bar twists, it rotates the inside of the spool valve relative to the outside. Since the inner part of the spool valve is also connected to the steering shaft (and therefore to the steering wheel), the amount of rotation between the inner and outer parts of the spool valve depends on how much torque the driver applies to the steering wheel. " ......This is the spring to which Dr Bob refers . The spool valve is the key to operation but has nothing to do with external power steering leaks.



Animation showing what happens inside the rotary valve when you first start to turn the steering wheel
When the steering wheel is not being turned, both hydraulic lines provide the same amount of pressure to the steering gear. But if the spool valve is turned one way or the other, ports open up to provide high-pressure fluid to the appropriate line.

 

Sure bob. I will try and take some pics.

 

I got the later model rack installed the day before our trip to SITM. IMHO it was well worth the extra $. I can't be sure that the rack that I replaced was working properly because every now and then it felt like it would bind. It would just catch at random spots when turning and once I forced it past the catch point, it seemed to do ok. It was very intermittent and sometimes would go days without acting up and other times it did it every time I turned the wheel. It seemed to happen less often after the new motor mounts were installed but that may have been wishful thinking on my part. When it didn't bind, it seemed to work as it should. Anyway, the required steering effort has been greatly reduced with the new rack. I replaced the tie rods as well but haven't yet installed the HO Griffiths pump. Once I get my rear end straightened out, I'll put the pump on and see if that makes a difference as well.