Steering play

[robdimond]

I've been on a saga over the last year tightening up the steering on my S2. So far I have replaced (all worn in some way and in need of replacement)

• Offside track rod
• Front wheel bearings
• Steering shaft with U-joints
• Front struts

I'm still not happy... it's possible for the rack input shaft to move 5 degrees either way without the track rods moving. I can only assume that this is an acceptable and normal amount of slop or that the rack and pinion are both worn. I think my next move is to replace the rack since rebuilding will not do anything to fix the wear on the gears.
Thoughts? Am I being unrealistic about how 944 steering should feel?

 

[ShaunHenstridge]

Hi, whilst I can't offer any help with the issues you have, you may (or may not) be interested to hear that I have a spare S2 steering rack. It's off a Concours S2 cabriolet with 55,000 miles on the clock and hasn't been used on a wet road for 15 years. I've only owned the car for 3 years, but when I bought it, the steering felt stiff and on tight, slow turns, the steering didn't self-centre. I tried a number of low cost options, but none worked. It was suggested that it may be the steering rack, so I bought a brand new one and had it fitted last March. Sadly, it made no difference at all! I planned to sell the old rack to cover some of the cost, but didn't get around to it. If this would be of any interest to you, please let me know.

 

[robdimond]

Shaun,

Very interested... I think I've eliminated everything except for the rack. I know from the original owner that my car has been through four racks in it's lifetime! I will send you a PM.

Rob

 

[Richair]

It doesn't sound to me like you actually have a problem, as hydraulic PAS racks have an inherent degree of rotational 'play' as this is how the valve mechanism works.

The pinion shaft is split into three parts: an upper and lower section joined by a slotted key with a central torsion bar which acts as a spring. The pinion shaft assembly sits within a barreled rotary valve. As the driver turns the wheel the pinion shaft twists which opens a valve to apply fluid pressure to the rack piston which results in a reaction at the rack. So whilst the pump is running the drivers will not notice any free play as the shaft only needs to twist a very small amount to induce a reaction. However without any fluid pressure there's no reaction at the rack piston so the pinion shaft will flex by the full amount permitted by the key joint.

I know all this as I currently have my 944 PAS rack fully disassembled as I'm properly converting it to an unassisted rack and removing the rotational play. Here's a few pictures to illustrate:

 

[robdimond]

Hi Rich,

That's interesting... but it doesn't 'feel' to me like a torsion/spring element is being twisted... it's quite loose and has something of a rattle to it if you rock the steering wheel to and fro. The steering also doesn't feel right on the road... as if too much correction is needed to keep the car in a straight line. I've not driven another 944, but they are meant to be great in this department which makes me think that something is amiss.

Rob

 

[Richair]

Ah right oh, if you're feeling it on the road then it sounds like you do have an issue somewhere then. How many miles has the car done on the rack?

If all the ball joints are tight (any 'looseness' in the joints will transpire into more significant deflection when loaded) then it most probably is the rack. So a refurbed one or a low mileage one would be well worth trying. I've chased down steering issues in the past only to arrive at the rack at the last resort but it solved the issue; the symptoms experienced were as you describe.

For reference the rack in my car has done 118k miles and has very little internal wear and felt perfect for a power rack and I'm very fussy about steering feel. Plus I've found the 944 to have up there with the best in terms of steering feel and I've owned and driven some very well respected cars for their steering 'feel'.

Just to eliminate the obvious, but I take it the car has been recently 4-wheel aligned? It's surprising how much difference poor alignment can make to the feel and handling of a car.

 

[zcacogp]

Geo is indeed a good thing to look at, as Richair suggested. Also, do you have the 968 caster mounts or the old 944 ones? Fitting the 968 items to my S2 sharpened up the steering feel considerably.

Oli.

 

[robdimond]

Thanks both. 944 castor mounts... I was considering an upgrade to 968 parts.

I've no idea how many miles on the current rack but I know it went through three replacements between 1989 and 2009! It must be due one!

I had the alignment done before I replaced the front suspension... so it is out now but I wanted to get everything sorted before going round the loop again.

 

[Richair]

No car should have had that many racks unless all of them were knackered high-mileage replacements. The ZF rack fitted to our cars seems to be quite a robust item!! I'd expect one to last 150k at least. But then of course they do leak so it could have been replaced due to that. The proper way of sorting leaks though is by replacing the seals not by fitting a second hand rack that will inevitably leak.

Shagged castor mounts will affect steering feel a little bit but I'd say not by as much as poor geometry. Do both, double check the tie rod that hasn't been replaced and see where that gets you. Make sure they 'pin' the rack when setting the toe.

 

[zcacogp]

As Rich said - change the mounts and have the geo done. (And change anything else that may need doing as well, such that the geo is done last, natch.)

FWIW, my S2 is coming up to 200,000 miles and the steering feel hasn't changed noticeably in that time (although any change would be progressive, so I'm not sure I'd notice it.) I'd certainly hope that a rack lasts more than 150,000 miles though.