[Saloon-lovers] Adwest Power steer MKX/420G/Landrover

It has come to my attention that the Seal kit for the Adwest
Marles variamatic steering box in 4.2 MkX and 420G, matches
the part numbers of the seal parts/kit for a Landrover
Defender/Discovery/Range Rover.

The parts and kit look the same in pics.

This is very curious, and suggests to me that they must be
very similar in construction?

A clever fellow shows how to change the lower internal seal
(the ‘‘blue seal’’ that leaks) without stripping the box (as
per the manual…a fearful job apparently)


(think you have to join up to view the pics though)

the attached quote is from that discussion…a Range Rover owner.

The article above helped me. I hope I can help other people.
I’ve Range Rover classic with a steering leakage on the same
place. On the net I searched on the string ‘‘seal 605-45135’’
and came to this article. To try to solve the leakage I
bought the landrover kit ‘‘STC2848’’ from Bearmach (number
15590004 from Corteco) for about 5 Euro’s (by now
paddockspares 3,06 English pound exl vat). The kit contained
the blue oil seal (605-45135) ,mentioned in the article
above. Also the kit contained an extrusion washer (rubber
and metal and number 16), Dust seal with number ‘‘AS 10780’’
and a circlip. De combination seems the lower row in the
picture showed in link
The order of the parts in the lower row is the same as in my
power steering. I hope helping some one.’’

It would be very interesting to find out exactly how similar
these boxes are to Jag–
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In reply to a message from awg sent Tue 5 Nov 2013:

When I rebuilt mine last summer the seals kit I had
included one or two bits not listed in the Jag
I believe the box was also used on some Rolls Royce
models - the Hobourn-Eaton pump definitely was. I used the
420, and range rover shop Manuals as references and iirc
also the rolls royce. One of These three also includes
Information about how to adjust the trim screw (which the
Jag Manual says not to remove or Change (under threat of
Being me, I removed the trim screw during the rebuild -
there are 1 o Ring and 1 Teflon seal on the valve shuttle
that can only be renewed by taking the shuttle off the
Torsion shaft, and this in turn required removing the trim

The original message included these comments:

It has come to my attention that the Seal kit for the Adwest
Marles variamatic steering box in 4.2 MkX and 420G, matches
the part numbers of the seal parts/kit for a Landrover
Defender/Discovery/Range Rover.

1968 3.8S
Zurich, Switzerland
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Hi Andrew,
I am battling with converting my MK2 to Power Steering, and have a used Adwest box which I suspect someone might have played with. I think I need to adjust the trim screw as it pulls to the left, do you have any guidance on how to do it? Also which manual has the information how to adjust the screw, I have not been able to track any down.


Personally, I’ve no experience of working on these boxes, though I am looking for one and the associated steering gear to convert my Mk2. I’ve seen the link above widely quoted as helpful in servicing them. From what people say, they are easier to rebuild than the Burman boxes they replaced.

To avoid pulling, isn’t it important to centre the box before setting the track rods?

It would be useful to know how close the Jaguar system is to the later one used by Land Rover. I’d ask Adwest, who would do rebuilds for you, but sadly they closed the factory a few years ago.

Google “youtube rebuild adwest steering box”, and there is about 6 videos, showing a Land Rover Defender box being rebuilt.

They are identical in design to the Adwest box used in 4.2 MKX, and 420G, 420, some MK2s, some S-types

The information on the trim screw is contained within these Service Manuals, including the 4.2 MKX

Are you sure the vesicle pulls to the left, and the steering wheel is not incorrectly oriented so that it has to be held at an angle, which can mean a few things, including the steering tie rods and draglinks are not set correctly

FSM details for adjusting the valve bias trim screw within the steering box suggest it should not be attempted, it would require the box to be removed and stripped down, and all parts checked

Unfortunately Andrew is no longer with us to give sage advice, except in memory

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They may be identical in design but I doubt we could be so lucky have any of the much newer, and less likely worn out, a direct bolt in replacement to any of our 50+ year old Jaguars.

You are correct

While the internal dimensions are identical (same seal kits), the outer body has different bolts holes for various models, and the shaft and worm, while being the same diameter, also are slightly different

I have a spread sheet comparing the part numbers of various Adwest Jag boxes

The internal and external seal kits are somewhat cheaper if purchased as Land Rover items instead of from Jaguar suppliers

Anyone wishing to rebuild one should look at the Adwest vids, I dont know why my links have disappeared, some are still available on Youtube, I downloaded them all a while back

Hi Tony, Thank you for your response. I am pretty sure that the geometry is correct and the box is the issue; when I have the car up with the front wheels in the air and start the engine the steering wheel turns firmly to the left, which cannot be correct. You can turn it back but are fighting the hydraulics, and on the road the car pulls to the left but is otherwise ok. A bit of background, I bought a complete front end from a 420 being wrecked. I installed the assembly, found a MK2 dynamo steering pump, and on the road the car would lurch from side to side which was a bit scary, and it leaked fluid from the steering box. I stripped the box, following the manuals and videos, and there was play between the torsion rod and the input spline on the valve and worm shaft which is a no no, and would explain the lurching. I fixed that (removed the pin, drilled and reamed to a slightly bigger size, new pin, no play). New seals, now the car pulls left a bit and it still leaks quite a lot. So next step is to find the leak, but I have a horrible suspicion is coming from between the torsion rod and steering shaft input but it is really hard to see. The leak and the offset might possibly be connected, but I can’t see how. So any ideas on other causes that might make the steering try and turn itself to the left would be welcome. All the manuals that I have seen just say don’t touch the trim screw, just buy a worm assembly which is a bit hard these days. However there are a few references out there to a method of setting the trim screw, but I can’t find them. Any guidance would be welcome

ok, you have been deep inside it

there is info in the MKX manual (and maybe others) on how to apply a pressure gauge, and to adjust the trim screw if necessary, and other tests, but at the end of the day, it sounds like you have a fault in that area

I do believe Andrew may have said he had a similar issue, took apart the valve mechanism, and found a cut o-ring or maybe Teflon inside

You may wish to search every occurrence of “adwest” and his ID

I fear this may be an issue with my replacement box, which has too much freeplay,
I have adjusted both the screw and locknut on the top, and the big 1" screw in the side and there is still too much play at the wheel

My previous box leaked too much, and also had play, so I swapped, but looks like I lucked out. I do have another, and it does not seem to have freeplay when tested out of the vehicle, but that can be deceptive

Its a seriously unpleasant job changing the steering box on a 420G

To find a leak, what I do is clean suspect area spotless, then dust with talc powder or even flour will do, use for a very short time, maybe 2 minutes, check for stain

its a pita to clean it that well, white rags to finish

Thanks Tony, it is not a lot of fun pulling the box out on a MK2 either, biggest issue separating the lower steering column, I have to take off the carbs to get assess, even to see it. A few posts on this elsewhere. Will try the flour trick for leaks, but only for a few seconds as the leaks is quite bad. Will keep you posted on progress, need to get some motivation first.
How much play do you have in your steering? From memory the rule of thumb was about 3" of movement at the steering wheel (engine off) before seeing a bit of movement at the wheels. That’s about what I have setting it up by the manual with the box out of the car, there is a reasonable amount of preload that needs to be applied to both adjustments.

I have between 1" and 2".

The FSM specifies about 1/2"

The Adwest system on my vehicle is incredibly light in the straight ahead position, but I believe that is the way they are designed

It is definitely in the box, all other parts are renewed, and I can visually check that the input and output shaft there is a delay

Its ok for me, but the registration mechanic is uneasy

I think I will strip down the old box and see if I can work out exactly what goes on in there. All steering boxes tend to wear the main gears near the straight ahead position, as thats where most of the use is

If its the lower seal, you can detach the Pitman arm, and spit the seals out using hydraulic pressure, rather than rebuild the box

So do you determine the play with the wheels or the ground or in the air? Mine has about an inch with the wheels up, but there is a little play in the steering column joints which I will fix. My box is tightest in the middle with no play, and a little play at the ends which does not unduly concern me. However I did have to adjust the shims on the valve and worm assembly to make this so. The leak was coming from one of the hoses, just needed to be nipped down a bit more so a relatively easy fix.

I follow the exact instructions in the FSM, which is to lift the front wheels and look at the Pitman arm while rotating the steering wheel (not as easy as they make it sound, would not work if you were vertically challenged)

My understanding is the sector shaft gear and worm gear may have some wear that allows this free play, as both screws are adjusted to maximum tightness

It may be I can gain additional tolerance by removing a shim, as you allude to

You have an advantage in that you have had the box apart, in my case, once I have it apart, hopefully I can understand things better, I will take apart my original box first

Its not at the top of my priority list, and its the sort of job needs an uncluttered work space and some time and patience

I originally swapped the box out cause it had a bad leak in lower seal, which was not fixed by a seal change, and it had a couple of other issues, I had a spare on hand

Did you read the section in the FSM on adjusting the Trim Screw in situ ?

I was unclear on how that would be done

If you have not read that and wish, I will post the relevant section up on here

It sounds like your FSM is more comprehensive than mine for a MK2. I guess this is because most Mk2s do no have PAS and so PAS only merits an addendum. I would really appreciate it if you could post the relevant section on adjusting the trim screw in situ.
Pulling the box apart and reassembling with new external seals is relatively easy. Repairing any worn or damaged components is more tricky, as my manual simply says replace anything not right. I elected not to replace the internal PTFE seals as specials tools are required, I could make these up but the seals looks to be in good condition so I left them, but I can see that these would cause a trim issue if they leaked. Fortunately the seal surfaces on the input and output shafts were in good shape, but the old seals were very hard. The small bearing at the back of the worm is not great, but I have a fix for this if required later.

Hopefully you can make some sense of that

One thing I will add

I did make a special gauge to do my BW8 trans, which needed a specific fitting & relevant PSI gauge off eBay and 2 metres of hydraulic hose, so you may consider to do this if you are feeling serious.

The gauge and fitting cost less than $20, the most expensive part was the hose

Thank you Tony, it does make sense and is most useful. It explains what the plugged port on the top face if for, I did wonder. I will follow the method without a gauge, and if needs be install a gauge and repeat. The internal leak check does not require a gauge is probably worth doing as a check.

No worries Nick,

keep us informed, as you do seem to have good mechanical knowledge

Not many folk know much about these boxes, but I would say that possibly joining or searching a Landrover forum may be useful, only because there was so many more put into Landrovers than Jags, so bigger knowledge base (hopefully)

Thanks Tony, I used to do this kind of stuff for a living, but not on cars.
The procedure worked well enough although access is a bit challenging, and I was able to trim the unit out ok and the car drives ok. Steering is light, but I think that this is the way that they all were, certainly compared to modern cars. It does not wander which is good, but still some fettling to do to finish off the job.
Having done the job some advice for anyone else tacking this Adwest box trimming task:
-The plug in the adjustment port was very tight, so make sure that you have a good Allen key (5/32" or maybe better 4mm), and clean the muck out of the hex plug to get the Allen key right in. It would be a disaster if the hex gets rounded, or if you drop and lose the plug.
-The trim adjustment position is exactly 180 degrees from the straight ahead position on the steering wheel, I found it best to mark the location on the box before removing the plug. If you turn the wheel with the plug out copious amounts of fluid squirt out; the job is messy enough as it is.
-All the time the plug is out fluid is weeping out, so best to be prepared. You need a flat bladed screwdriver no bigger than about 6mm to get into the port, it goes in quite a long way. The trim screw is not particularly tight when you manage to get the screwdriver located in the slot.
-I found that turning the trim screw clockwise makes the car turn more to the right. It did not take too long to find the right settling (maybe I was lucky!). My criteria was that the wheels stayed where they were left across the full range (engine running), roughly equal steering wheel effort to move in either direction, and I did try the test of moving the wheels in both directions to check for equal effort which seemed ok.
One other question that puzzled me on the Adwest box; for both manual (non PAS) steering and the Burman box setup there are external stops to limit the movement of the steering at both extremities. There is nothing on the Adwest setup, so I assume that the effective stops are from the box, i.e. when the piston bottoms out at each end. This strikes me as odd, or am I missing something?

I dont know, but I only learned fully about the trim screw adjustment procedure when I posted it up for you, even though I have read the relevant chapter, which may have additional details on your question

Good to hear its improved

I find the steering to be extremely light on these cars, too much so, but I thinks its partly the design parameters, partly wear due to age

As I said , I will probably dismantle my original box so I can understand what is inside, its quite difficult to estimate free play between input & output shaft