Vicarage rack pinion conversion

[geoffxk888]

Hi I'm having to convert to a vicarage rack and pinion system - who out there has already done this?
I would welcome any feedback on both how easy it was and what the result was, I'm told it makes it drive more like modern car
Cheers
Geoff

[ChrisDixon]

Hi Geoff I have the Wilkinsons kit on my 3.8S which uses an XJ6 series or XJ-S rack. Fitting involves some compromise to the steering geometry for 2 related reasons, the need to cut the track rods because the Mk2 has a narrower track, and the lack of space between the rack and the body which means the rack can't be mounted further back. This results in the car driving and handling well once the steering geometry has been correctly set up, which requires some trial and error as the factory settings for the steering box are not ideal. Toe, camber and caster all need to be considered. A compromise on mine is less self centring than I would like. You notice the compromise when manoevering ar slow speeds, as the tyres tend to drag and squeal because the relationship between outer and inner wheel tracking (or so called Ackerman) is compromised, also the turning circle isn't great. That said I am on standard 185/15 Vredesteintyres and others may report different findings if they are using more modern tyres.

I see that the Vicarage kit uses XJ40 rack, again a car with a wider track than ours. I don't know how they run the hydraulics (Wilkinsons use a clever electric pump which requires an uprated alternator), or whether they would claim their setup is better than the Wilkinsons one. But the questions I would ask are generally about geometry (specifically Ackermann). If you can, try and arrange to drive a car so equipped to ensure you like it.

By the way, why are you "having" to go down this route? I've heard you can obtain "quick" steering boxes to which electrical assistance can ve added if you need it. I also recall someone suggesting using a rack from a car with a similar track to the Mk2, a Mondeo perhaps, or was it a Montego?

To make a Mk2 drive more like a modern car you'll also need some other mods if you haven't got them already.

Hope this is of some help. Chris

[B87UL]

Geoff

I have a 3.4S that was already fitted with a Vicarage power steering conversion when I purchased the car. In this case the power source is provided by a dynamo driven pump as per the original factory version and the car has factory size 185 x 15 radial tyres.

Luckily, I have available at home, a four-post lift with 2 tonne travelling jack, weaver turntables, Dunlop tracking gauges and castor camber measuring facilities together with some 60 years of automobile experience and consultancy work Worldwide. This equipment provides all the measurements needed to statically assess the steering rack conversion.

Chris has described the situation very well. However, the steering lock can be increased with some fettling and attention to the front suspension top joint area and trimming the brake disk shield at the top. It is in that area that the steering lock is restricted by disk contact on full lock, probably caused, in my case with minor tolerance issues on components changed over the years.

I favour the rack and pinion conversion although it has limitations, some like the lack of “toe out” on turns can be bettered a little to stop tyre squeal, but cannot be eliminated. Fitting a rack and pinion is a compromise on these cars. It is this problem that results in heavier front tyre wear, but both wear and squeal can be suppressed somewhat by arranging to just provide toe out in the straight-ahead position. This cannot be done just in isolation, castor, camber AND the ride height front and rear needs to be set correctly. Vicarage advised me to set castor to 3 degrees positive for example, but doing so appears all but impossible as the shim adjustment even at maximum is not 3 degrees. This is still an ongoing issue on my car as presently I have the rear end out of the car (3.4 S) and I am taking the opportunity of correcting the rear ride height a little.

Notice that Jaguar used steering idlers to attain both toe out on turns and nearly zero bump steer and no amount of jiggling about with rack lengths, any rack, will solve these issues. You will undoubtably come across owners in other threads who will try to convince you that the steering rack issue can be solved by changing the racks. I assure you it cannot, the problem is shear room between the engine sump and steering rack, if you get the bump steer correct you have the toe out on turns incorrect.

Chris mentioned he would prefer more self-centring, that is a problem I experienced and increased self -centring is on my to do list, as is limiting the hydraulic pressures, which is one of the causes. In my case I find the car oversteers but this is a condition I can live with and I will eventually improve upon. The oversteer is not helped by the very high gearing to the steering on my car, other drivers may on the other hand find the gearing to their liking at about 2.25 turns lock to lock.

If you are contemplating fitting a rack conversion yourself, I can only tell you what I see on my already converted car and describe the main issues. I have assumed you have all the components in a conversion kit, but you may decide to improve the conversion, say by using special heat insulation on the hydraulic lines. Much depends on what equipment and skills you possess besides the physical room available.

Initially it will be necessary to remove the old steering linkage and the steering box together with the dynamo, the latter will need converting to accept the hydraulic pump unless you go the electric pump route. Removing the battery would be mandatory and you may need to remove even the clutch slave cylinder to improve access. If needed, consider adding another battery rather than converting to an alternator.

As you will need to detach the steering column lower joint, I would suggest you replace the steering column bushes and the horn slip rings and bushes. You might even consider replacing the throttle bulkhead shaft bushes. All these replacements produce a much better running car and are fairly cheap and easy to replace when the steering column is removed.

A section of the chassis is cut away and re-welded, using a template, to clear the steering rack pinion area. In order to achieve reasonable access, I would think that it is necessary to drop out the front subframe and remove the rear carburettor at least, but you might just achieve the cutting out and welding with the frame in situ. Removing the sub frame in any event would help to position the two special brackets that attach the steering rack (ex XL40/XJ6) to the front sub frame. You would need to take precautions to prevent damage to fuel and brake lines during welding.

As an aside almost, the condition of the engine mountings may be of some consequence if they have allowed the engine to drop when sump to rack fouling may be another problem to solve.

I trust these notes may help.

Norman

[ChrisDixon]

Ah yes i had forgotten the dreaded bump steer. And any play in the column will be exaggerated once a rack is fitted so Norman's advice should be heeded. Someone set my car up badly and the tyres would squeal going over a speed cushion, and the inners were wearing within a few hundred miles. My rack had to be replaced a few years back, perhaps due to excess strain on the rack due to the aforementioned geometry issues. On changing mine I found that the replacement once fitted along with new mounting bushes caused the lower column joint to foul the chassis leg so I had to grind a bit more out of it. Later I discovered the engine mounts were shot, and alarmingly, the front subframe mounting lugs had sheared.

Now everything is sorted the car handles pretty well, also thanks to firmer springs a Harvey bailey kit and some polybushes. If I were starting from scratch I would seriouly consider the alternative of a high ratio steering box. I think I even got a price a while back when I was contemplating removing the rack, which I don't recall but I don't think it was that expensive (the company is called ICS who reverse engineered a Mk1 box)

Someone jokingly suggested that if I wanted decent steering I should buy an XJ6 S1 ... which I went and did but that's another story.