Jaguar Mark 10 4.2 steering box

I am trying to fid a steering gear box for a 1965 steering box for my 1965 Mark 10 4.2. Not sure where I can get it rebuilt or need to replace it.

being a 4.2, you should be fortunate to have the Adwest power steer box

I understand these may be repairable, as they are almost identical to various Landrover steering boxes,
depending upon what is wrong with it

I personally bough a whole wreck minus engine & gearbox for $300, just for the steering box and a few other parts that are difficult to obtain any other way

I have seen them on ebay, including very recently they wanted $550 for the whole front end

my understanding is LHD items are very scarce

If it’s a Varamatic, then you can rebuild it. I’ve rebuilt a couple of them. Not really all that hard to do if the only problem is seals. If the hourglass is worn then it’s a different story.

I used a combination of manuals during the rebuild, including the LR one.

How can I identify the brand it is.

they look different, all 4.2 should have the Marles Adwest Variamatic

3.8 had this

cant remember manafacturer, MK9 had them as well

look at the top cover will tell you

what is the issue with yours?

I have 2 420G cars and the one has the top version and the other the bottom in the pictures, so I guess some 4.2s also had the “3.8 version”.

Parts Manual, Thorley and other references call out all 4.2 as having Adwest

brand of maker for earlier units is Burman

it is possible the steering box or front end has been swapped out?

the “usual” situation is someone swaps out an entire front end, or box of a failed 3.8 box, for later units

however, if your vehicle had a failed steering box, someone may have fitted the early unit,
cause they had access to one?

4.2 vehicles have a different PS pump also, same as XJ

420G box has some slight external variations, as per FSM

when input torque is applied, the rack and piston can be seen moving for-aft about 2mm, the large c-clip retains the assembly.

Is this normal?

can it be adjusted?

Hmn… I’m probably not the right person to ask for a definition of “normal”.

Do you mean that the cover moves?

If “YES”:

No, it can’t be adjusted. The good news (if it’s doing it with pump pressure applied) is that it means that the seals at the Cylinder cover (18) and the rack piston (15) must be good.

The piston is dual acting, the torsion valve applies either equal (return) pressure to both sides, or more (pump) pressure to one side or the other of the rack piston. Working correctly there is no “vacuum” which could be pulling the cover in, and if the piston is moving away from that cover, then that is because the valve is applying pump pressure to that side.

If “NO”:

If you’ve got it on the bench and the cover is off, then yes, the piston should move back and forth when you apply input torque - the input shaft acts on the rack via the angled roller wheel and sector shaft - but it should move more than 2mm. It’s more like 1-1/2" in or out from the center position.

yes the cover, box is in car. No oil leaks out in that spot

there is too much freeplay at perimeter of steering wheel before Pitman arm moves.

lower shaft seals are also leaking like a sieve.

I am going to squirt the seals out the bottom of the shaft in situ, tighten up adjustments

there are 2 adjustments, one presses down from the top, the other release a grub screw and turn the 1" diameter screw, which appears to bear upon the rack&piston rear surface

The freeplay adjustment is the threaded rod with stopnut on the cover, this adjusts the mesh of the roller with the hour wheel. The large screw adjust the depth of mesh between the sector shaft and piston (also free play related).

There is also a bias screw in the torsion valve, which is under a grub screw.

If it’s just weeping then (all) new seals will probably fix it, if it’s leaking massively then new seals might fix it too, unless things have become bent or worn inside.

My experience is that it’s faster to get it on the bench and tear it down and fit new seals than it is to lie underneath the car swearing at it. (I’ve tried both approaches).

On the 420G, the steering box has the whole engine weight on its long mount bolts which also go right thru the I-beam

a true son-of-a-sl*t to R&R the steer box

Once it’s out, not really. Somewhere between dialing a Diff in, and rebuilding a gearbox. (I did mention that I’m not “normal”)

More than amply compensated for by the lovely mirrors on the hamburger trays in the back, and the flattened ovoid shape of the toolbox.

I don’t remember taking it out of the 420g being all that difficult, but then again, I was still in my teens, so I may be repressing some of the memories.

maybe you had a pre-'68, in which case the problem does not exist, as the engine mounts are upon the sheetmetal, not the I-beam. The engine mounts on 4.2 was relocated on the block in 1968

The engine weight must be lifted and the IFS “wiggled” to get the steering box bolts to go back thru,guess how i know.

If I do have to pull the steering box, i have a couple off spares, so hopefully can achieve one without worn parts.

I will soon attempt to spit the seals out down the Pitman arm shaft, using the hydraulic pressure of the power steer pump, and fit the $20 Landrover seal kit, which has the same seal part nums as the Adwest 420G, so wish me luck

Luck isn’t going to help, what you need is vocabulary. Bosnian seems to be the most effective, followed by Croatian, Slovenian and Romanian. German is completely useless for cursing.

Mine was late '68, I took the box out with the car on the driveway with nothing more than breeze blocks, wood, and a hydraulic jack, and regular high school English, but I was a lot younger.

Bite the bullet. You’ve got enough spares, rebuild one to spec, possibly even bench test with pressure, then swap it.

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thanks Andrew for sending me those docs, which you had already helpfully sent

With regard to the selector shaft adjustment screw, pointed to in blue, and referred to in your patents;

Am I correct the adjusting screw actuates a cam that tightens the selector shaft roller against the worm?

This selector screw only moves thru ~90degrees, it cannot be turned either way more, so i assume the cam only has a limited capacity to take up slack

at this time, I cannot remove circlip 33 from below the selector shaft…it is very tight, the shaft is wide, and a deep groove means no pliers will compress it enough to release from the groove…unless i can get the clip out, the whole box will need to come out, (to replace the leaking seal)

getting the c-clip seems a tricky 2man job on a bench, but i know it can be done from below somehow!

the area circled in light blue, there is a bronze bush in the case that the shaft rides in, if that bush is worn
I do not know whether a replacement can be obtained?


There’s no cam. The adjusting screw moves the whole sector shaft up and down. This allows you to adjust the depth of mesh of the angled roller with the hourglass. The Screw is held captive in the end of the shaft by a circlip iirc, and you should be able to rotate it freely once it’s out of the box. It may be gummed up, or worn. Once you install the locknut then the shaft can still rotate about the captive end, but it only moves about 90 Degree (or whatever the sweep angle of the output end is limited to).

The circlip is easy to get out if you hold the box in a vise by one of the lugs. There is a hole drilled in the periphery of the cylinder so you can get a punch in and push the end of the circlip. This presuming that the guy who last assembled it put the circlip in so that one end is only 1/4" or so past the hole - if that isn’t the case then it may be a bit of a character building exercise… Lube everything up and use a punch to spin the circlip until one end is 1/4" past the hole.

If the bush is toast then you’ll want to find a tool and die maker to remove the old and fit and ream a new bush for you.

are you thinking of the big clip in the cylinder about 3" OD ? (item 20)…I mean the output shaft circlip which is only about 1.5" OD…(Pitman Arm shaft) (item 33)…I will check to see if any slot in case in that location, also take it to my mechanic mate, put it on a hoist, and hope he has superior c-clip pliers

hopefully I can remove the c-clip, as i just road-tested the car after all slack has been taken out and it is satisfactory/good…there is no access hole for C-clip 33

Much of the slack was in the Pitman arm, dont know why, but one of its clamping washers was ~0.5mm too small ID, catching the splines and allowing the Pitman slight freeplay up & down the shaft.

This could only be detected with an assistant at the wheel

the washer has been honed out, and it has reduced freeplay at circumference of steering wheel to near spec of ~1/2" compared to maybe 2" before

I was indeed thinking of the big clip (#20). Now that you mention it I dimly remember #33 being difficult to get out. The groove was very deep and there was only a tiny bit of hole reachable at the ends as I recall. Same with yours?

The seals kit I had contained quite a few bits were excess when I was done. One such bit was a big rubber buffer which seemed to have been meant for under the Pitman arm.

yes, even when fully compressed against the shaft, the clip does not disengage from the groove, so cannot be pulled down, the pliers continually slip out of hole.

normally in these cases, I pry something sharp in under the corner of the clip and wedge it out.
It has to be fully compressed to allow this

because the clip is so strong, it is very hard to compress with one hand
hopefully, using a hoist, and mechanics Snap-On quality pliers, one of us can compress the clip, while the other pry at it

otherwise I will need to remove box it and do the job on the bench, and it will still be difficult

I got the idea from another lister, so i know it can be done