Hydraulic Gear Selector - Strip Down and Overhaul (Part 1)

Having bought the rebuild kit several years ago, I have eventually got round to rebuilding the bvh 'hydraulic gear selector'.

The 'hydraulic gear selector' of a hydraulic gearchange car

The first thing to say, is that I don't call this the 'hydraulic gear selector'. That's what Citroen and the manuals call it. I've always called it the 'gear brain'. It interprets the movement of the gear wand (yes - I call the gear lever the 'wand') and translates that into the selection of the relevant gear. So it's a brain - right? A hydraulic gear selecting brain. 

 

It's also worth noting that the unit is actually two devices - the main 'gear brain' and also a 'gearchange speed regulator'. This second device was introduced to deal with changes in fluid temperature and pressure that would otherwise alter how the gear brain responded. And I don't call it a 'gearchange speed regulator' either. I tend to call it a 'viscosity compensator' or 'viscosity regulator'. Take your pick....... In stripping and rebuilding the 'unit' I will deal with each of these devices seperately. Anyway, mine was (were) looking decidedly shabby. 

'Hydraulic gear selector' and 'gearchange speed regulator'

The paint had fallen off the aluminium body and the steel part had surface rust. I was keen to clean it out  - partly because it seemed like a good idea and partly because I'd previously had clutch problems and so wanted to rule out the gear brain (told you) as a possible cause as well. 

 

Workshop Manual Instructions - A Cautionary Note

English language instructions for stripping and rebuilding the gear brain can be found in manual 518 (which dates from 1966) and you will find the instructions there at step 25 onward of Operation DX.334-3. The instructions were not originally included in printed copies of English language manual 814, though you may find they are added into PDF copies from manual 518 - which dates from 1966.

 

Where the 'gearchange speed regulator' is concerned, you need to be aware that while the instructions in French language manual 583 (volume 3) are correct, the instructions (and photos) in the English language manual 518 contain several errors!  For a good few years these errors have been left as-is in digital versions of 518 (and 814 where added-in) but, at the time of writing (mid April 2023) have been corrected to mirror the French instructions. If you have a PDF copy of manual 518 or 814, then depending on when you downloaded it (and from where) the English instructions may (or may not!) have been digitally corrected. Unfortunately the one weakness of the digital versions is that here is no version control on the digital versions  - so you don't know what may have been added or updated. If you want to keep a downloaded local copy of the manuals, you really need to download the 'current' copy every time to be sure. Which kind of defeats the object.

Spot the difference: printed English copies of 518 have text and photo errors....

Last couple of point on the manuals: as the instructions are from manual 518 and 1966, they relate to cars with LHS fluid. The instructions tell you to clean and wash the parts in alcohol. For gear brains from LHM cars, the parts should be washed in petrol.

 

It's also worth noting that while the LHS gear brain instructions hold good for LHM carburetor cars, the gear brains of fuel injected cars are a little different. Mechanically I think the parts and construction are the same, but a noticable difference is how the 'viscosity compensator' is fitted to the top of the brain (more on that later). Anyway, overall there is enough common ground for the instructions to still be of use.

 

Initial Dismantling

I won't go into the details of removing the unit from a car. That is covered in the manuals. The only tip I will give is tthat's it's probably better to release the 'back' bolt of the double-bolt clamp connecting the gear selector lever to the slide valve of the brain (so that the clamp is left on the valve and gear brain - not the selector lever. The 'back' bolt is lined up better with the hole under the rubber bung and it just means that, when you come to connect it all back up, it's a little bit easier to tighten the bolt.

Double bolt clamp on the selector linkage

 When it comes to dismantling, the manual suggests you build a stand to hold the gear brain (stand 'MR. 3053-200').

Another Citroen 'Special Tool'.....

I just rigged something up with a piece of old angle. I just needed to drill a few extra holes for the bolts and to make room for the shaft that sticks out.

Home Made Stand

With the gearbrain mounted on it's end I first removed the gearchange speed regulator and the associated 'S' shaped pipes that join it to the gear brain.

Gearchange Speed Regulator Removed.....

With the viscosity compensator out of the way, the front end cover of the 'brain' can be removed. The 'front' being the end that points towards the nose of the car.

 

 

This cover holds a powerful spring for the syncro delay return pistons and the manual says each of the nuts and bolts of the cover should be released very gradually in turn - just one flat (of their hex heads) at a time. This is to ensure that the cover lifts off straight and doesn't snag.

Front End Cover

 I will confess that I didn't follow the 'one flat' rule studiously, but it soon became clear how easy it was for the case to jam on the studs and I did take my time on this stage. It was also clear how the stand helps to keep the unit steady and frees up one of yout hands - worth making one.

The front cover - released

With the nuts and bots removed, the innards (and the spring) were revealed. Also revealed was thick black goo and I was glad I'd tackled this job (remind me I said that later).

That is a BIG spring.....

 

.....and a dirty spring

Turns out the syncro return spring is actually two springs - one inside the other.

Second spring inside the outer spring

There are thrust plates on the ends. These are different shapes and it's important to note which goes where.

Syncro delay return springs

With the syncro delay return springs out of the way, the large main gear selector slide valve can be removed. You shouldn't need telling but be very careful not to drop or scratch this. Same goes for the shaft from which it was removed.

 

The gear selector slide valve

And with the base of the springs cleaned up you will see this....

Head of a syncro delay piston

It's the nipple end of one of the syncro delay pistons. On the end of the gear brain clamped to the stand, you will see the end of the 'auxilary clutch control slide valve' (or 'the auxilary clutch control slide valve' as I like to call it) sticking out. It has the hole through the end - for the hook of the auxilary clutch mechanism. This is it.

 

Tip of the 'auxilary clutch control slide valve'

Push this into the unit slowly and carefully and (with the end cover and springs now out of the way), you will see the first syncro delay piston stsrt to emerge from the top end. Again - be careful not to push this out and drop and damage it. Grab it as soon as you can and put it aside safely. Other syncro pistons will be removed and you need to make sure you do not muddle these up. they need to go back in in reverse order of removal. Citroen recommend that you make a little stand. I didn't do woodwork at school, so just carefully laid things aside.

Rack to store the pistons and other parts

With the first piston removed, you will find an 'O' ring seal in the circumference of the chamber. You need to CAREFULLY winkle this out. This is made all the more difficult by the seals being hardened over time. The technique I used was to skewer the seal with a dental pick and then pull it's edge in sufficiently to get something behind it. You need to be EXTREMELY careful that you do not scratch the surface of the chamber as this can ruin the gear brain. 

 

In this diagram, parts 12 and 13 are the syncro delay pistons and part 14 is the auxilary clutch control slide valve. The 'O' rings aren't numbered but are around parts 12 and 13.

 

Diagram showing the syncro pistons in situ

Right, with one syncro delay piston and seal removed, you need to do it all over again..... carefully push the end of the auxiliary clutch control slide valve a little further and another piston will emerge at the top end. (Remember not to muddle this piston with the previous piston). Now you need to remove the 'O' ring seal for the second piston. This is deeper in the chamber and less easy to get at. You need to take even more care with winkling it out. Things only get harder. 

It's increasingly hard to access and remove the old '' rings.

To remove the two remaing syncro pistons (yes - there are still two to go), you need to use a drift or similar to push the auxilary clutch control piston further up into the chamber. Once again, whatever you use, make sure you don't scratch the edges of the chamber. Removing the deep 'O' rings for the last two pistons is quite tricky and brings the most risk of scratching the walls of the chamber. Be warned! Finally, with the last piston and 'O' ring out, the auxilary clutch control slide valve can be removed.

I put the parts aside in seperate bags - marked so that I could make sure I put them back in the right order after cleaning and inspection.

Bagged and tagged......

With the stand having served it's purpose for now, I removed the gear brain and tackled the back end cover on the bench.This revealed another spring (not as big) and more goo (but not as much).

Rear end cover removal

Rear end cover removed

It's worth noting at this point  - and before atention turns back to the main body - that there is a 'secret' seal tucked away in the cover. I took a photo to remind me....

A note to myself....

Beneath the spring is a disc - a thrust washer - Under the thrust washer is the very tip of the automatic gearchange slide valve. (It's part 4 in the diagram earlier in this post).

Pushing the end of this valve SLOWLY into the shaft from the back end first pushes out a small plug from the other end (part 3 in the diagram). Don't lose this! Continue pushing SLOWLY and, one by one five small pistons will pop out in turn. NOTE: the slide valve will not, and should not,go all the way through the shaft

One of the small gearchange pistons starting to emerge

There are no 'O' rings to worry about this time but, again, Citroen say the pistons need to be replaced in the order in which they were removed - so don't muddle them up. Store them safely and carfully as, when the time comes, they will need to be reftted in reverse order. Finally, with the pistons out, the  slide valve itself can be pushed/ pulled out.

Removing the slide valve

Other than very carefully cleaning and preparing everything, that's 'disassembly'.

Gear brain parts

 

Rebuild kits are readily available. Some contain new springs, others do not. They all seem to contain a large number of small 'O' ring seals, but it turns out that these are just plate seals for the several hydrualic connections to and from the outside of the hydraulic gear selector. I mean 'gear brain'. 

There are a number of different rebuild kits available

Surprisingly, considering the complex job the gear brain does, it only contains five 'O' ring seals. But don't forget that the slide valves are manufactured to a fine tolerance interference fit. Plus you need a couple of replacement paper gaskets of course. My kit was simpler and cheaper and did not include springs.

 

Assembly is (of course) the reverse of disaasembly.....First the gearchange control slide valve was lubricated with LHM and carefully dropped into it's shaft.

 

Gearchange control slide valve

It should be a good tight fit but should not need any forcing.The thrust washer and spring can then be perched on top and a new gasket - brushed with LHM - was fitted. 

 

A new gasket was fitted

 And, of course, a new seal was put in the appropriate recess in the back cover (remember?).

 

A new 'O' ring for the back end cover

The new 'O' ring seal meant that the cover had to be lightly pressed (by hand) into place. The bolts and fixings were then tightened.

 

I put the unit back on my homemade stand.

Back on the stand

From the front end of the body, the five gearchange shaft was lubricated.....

  ....as were each of the pistons, that were then dropped in. These go in with the nipple end facing out of the hole.

Refitting the gearchange pistons

Lastly the small cap was replaced. If everything has gone back as it should, the top of the cap will be flush with the face of the shaft.

Now it's time to get back to those syncro pistons and tricky 'O' rings. This time job gets easier as you go along. The first thing to do is to refit the auxilary clutch control slide valve. This was lubricated and carefully dropped into the shaft. It slid in with a satisfying 'slurp'.The valve has a little circlip right at the end that stops it sliding all the wat through. It just sits at the bottom of the shaft, where it narrows, beneath the syncro pistons.

 

Next in goes one of the new 'O' rings. Lubricated with LHM, these can be manipulated in with a finger. Avoid the temptation to use anything sharp to get them to sit in the grooves. 

'O' ring for the syncro piston shaft

Next in goes a syncro piston. The last one you removed, should be the first one to go back in etc. Lubricated with LHM, the piston will slide down the shaft and sit on the rim of the new 'O' ring. It needs to be encouraged to go further.....I selected along depth socket that sat comfortably on the piston - but which was not so large that it would touch and damage the shaft walls.

Selecting a socket to help refit the syncro pistons

The pistons have a bevelled edge to help things along. I found that a generous brush of LHM on the fitted seal and when putting the piston in, meant that I only needed to give a couple of gentle hammer taps to persuade the seal to yield and let the piston past. It was obvious when this happened and I stopped tapping. I continued with another 'O' ring  and then another piston and gradually the stack built up - with lots of LHM to help things along the way.

Can you see the tip of the piston?

If everything has gone as needed, the rim of the last piston should be flush with the rim of the shaft. Like this.

The last piston refitted

The gear selector valve can be replaced.......

Refitting the gear selector slide valve

.....and then it's on to the home straight.

 

The last parts to fit are the springs and their thrust washers. An important point to note here is that, as the springs are compressed, the shank of one washer is presed into the body of the other. Citroen recommend that you check these for 'free play' to make sure they do not snag on one another and prevent normal operation of the gear brain.

The spring thrust washers fit together under compression

The other important point to note is that the shank of the thrust washer for the body end of the assembly (the 'male' thrust washer if you will) has a hole in it.

Note the hole through the thrust washer

The repair manual says that, when the spring assembly is fitted, it should be orientated so that this hole is 'towards the bottom' when everything is fitted back on the car. I took this to mean the hole should face down towards the ground and so took a few moments to work out what was the top and bottom of the gear brain when fitted. 

With that clear, the spring assembly was appropriately put in place and a new gasket added.

Nearly done......

The cover was carefully pressed-on - against the pressure of the springs - and the nuts wound on by a part turn. 

Refitting the front cover

I gradually added the bolts and gave each nut and bolt a small tighten in sequence - much as you would the nuts when fitting a wheel - until the cover was uniformly tightened down.

And that seems a convenient point to leave things. In my next post I will tackle the 'gearchange speed regulator' by which I mean the 'viscosity compensator' of course.

Steering Relays - Strip Down and Overhaul

 I finally got round to finishing the rebuild of the steering relays.

The steering relays help to transfer the movement of the steering rack to the pivot/ hub assemblies. The steering rack arms connect to the splined tops of the relay arms. The bottom cranked ends of the relays are connected to the pivots by a pair of arms and ball joint assemblies.

Steering relay parts

The procedure for removing the relays can be found at Operation DX.443-1 in manual 518. It isn't in Manual 814 as printed, but may have been added into some pdf copies of the manual from Manual 518. If so, it's in section 1 ('Removal and Refitting') in Volume 2. It's a similar story for the procedure for stripping and rebuilding the relays. You can find it at Operation DX.443-3 in manual 518, and those pages might be in some pdf copies of Manual 814.

Because of the job they do, the bottom ends of the relays  - down in the wheel arches - are quite exposed to rain and dirt.  I'd started to remove and strip the relays back in May 2021. As well as being dirty and rusty, with the steering rack removed and the hubs linkages disconnected, I'd discovered that the relays were quite 'knotty' and didn't move smoothly. 

The relays are held to the chassis by a large bolt passing horizontally through the chassis arm. The nuts on these are a real bugger to undo! Firstly they are on the wheel side of the chassis and so rust and seize on the bolt. Secondly the 'bolt head' ends are unconventional. In fact at first I didn't even realise they were bolt heads until someone explained what I was seeing to me. 

Bolt head of the relay arm bolt

The bolts are hollow. Rather than being hex-headed, they have only two, shallow, flat edges. To complicated things further, the heads are recessed into deep washers or spacers  - that's washers on the bolt end, not the nut end - meaning little of the heads remain exposed.

Washer (or more accurately spacer) on the relay bolt

All in all it means that there is a risk of rounding the straight edges of the head when you try to undo the nuts. I soaked mine in penetrating oil occasionally before I tackled them and proceeded cautiously. In the end it was pretty straightforward to remove them.

The relays are able to pivot/ be rotated to some degree around this large central bolt, and so are fixed in position by smaller bolts that hold the heads down to the chassis arms. When I removed these smaller  bolts I found a number of spacer washers.

The spacer washers are in the middle of the photo

These are spacers that pack out the space between the lug on the side of the relay and the chassis.

Spacing washers under the relay mount

It's all to do with the correct angle of the relay. When they are first fitted, a special tool is used to set the alignment of each steering relay.....

Use of tool 1995-T too align the relay.
(photo credit unknown)

The relay is rotated slightly until the pin engages in the dimple in the arm.......

Engaging the pin in the arm - more spacers needed!

......and then a combination of different thickness spacers is used to pack out any gap.

That's better...

I'm guessing all this is necessary because of slight differences in the construction of the chassis or differences in the machining of the relays - or maybe a bit of both. There could be a different number of spacers used on each relay - so keep them all, and don't muddle the relays up!

With the relays removed I set about dismantling. And things started to go wrong almost immediately. To stop it loosening, the edge of the threaded upper nut is peened over into a groove in the main body. I used a drift to bend that peened edge back in away from the relay body. I did that to both nuts.The upper nut needs a special tool to remove it. The tool needs to fit over the splined end of the arm and have four 'pins' that lock intro hole in the nut.

Relay nut. Note the peened edge at the bottom

The tool can then be rotated to loosen the nut. That's the theory at least. I fashioned a crude tool out of an old socket with four pins welded around it's circumference and tried to use a ratchet to loosen the nut - but it wouldn't budge without using considerable force and several repairs to my home made tool. It was heavy going with the noise and feel of metal grinding on metal. 

Daylight outside, but truly in the 'heart of darkness' now.....

I soon realised what the problem was: the nut threads had been damaged by the peening (and my bashing?) and were out of alignment - squashed or misaligned in some other way. My efforts at removing the nut were probably damaging the threads on the body too. With the nut half in and half out, I had no option but to try and press on. The nut fought me every fraction of a rotation. I used heat. I used oil. I used brute force. My workbench looked like a battlefield. And this was only the first relay! Eventually the titanic battle was over and slowly but surely the nut was removed. 

I tried to set my worries aside and I set about dismantling the relay. I was 'in the zone' and didn't bother to refer to the manual. With the nut removed, the arm had some freedom of movement in the body and the balls were dislodged from their bearing cups. With a bit of effort I was able to knock the arm out through the body. With it came some of the balls. The others remained glued inside the body with sticky, dirty grease.

With the top nut and relay arm removed, from the top end of the relay body I was able to winkle out the dished thrust washer, the top bearing cup and the top oil seal.

The top oil seal is beneath the bearing cup

On the bottom, cranked arm, end of the relay is a protective metal dust cap. That was carefully levered off to reveal an oil seal. That was prised out and, beneath all the rusty grease, was a circlip......

The circlip secures the bottom bearing cup

The circlip holds the bottom bearing cup in place. The arm bearing race - and so arm - is locked in position by that bearing cup but, with the circlip removed, the arm can be carefully tapped down and out. At this point I wished I'd referred to the manual!

All the grease and stray balls were scooped out of the body. The parts were cleaned and accounted-for before I examined them. 

Relay arm dismantled

Unfortunately several came up wanting.....On one relay, one of the bottom bearing cups was pitted in places.

Pitted old bearing cup  - and a new replacement

On the other relay, one of the ball channels in the arm itself was pitted.

Pitting damage to the bearing groove

In both cases I think this was down to water penetration and rust. Before I pressed-on with a rebuild I needed to know whether these relays could be salvaged. I used a file to try and dress the damaged threads on the nut and the body but the nut was still reluctant to fit back on without cross-threading. Once again, Peter 'Badabec' Bremner came to the rescue. A friend of Peter's had put the correct thread on a large piece of metal and I was able to run that up and down the relay body, like a heavy-duty tap, to clean up the threads.

Peter had also made his own pin tool. Much better than mine.

Peter's pin tool came to the rescue

With the relay body threads cleaned up and using Peter's tool, I was then able to run the proper nut up and down the body. Now knowing that I could at least reassemble the relays, I set about cleaning, painting and acquiring replacement parts.

By peening the edge over, the top nuts become damaged and really need to be replaced each time you rebuild.  Peter had rebuilt his relays (more on that later) and bought the last two NOS nuts available on Earth. No, really. I think he got very lucky there. I'd not seen them on sale before, and I've not seen them on sale since.  The DS parts suppliers sell refurbished units, so perhaps there is a source for replacement top nuts? Perhaps it's the kind of part Citrotech sell? 

On the plus side, Peter didn't want the felt dust seals from the botton of his new nuts and very kindly gave them to me. I left them to soak on LHM before fitting them - to give them a water resistant finish.

New felt dust seals

 

The felt seals fit on the underside of the nuts

I was able to find a pair of lower bearing cups for sale (these are slightly different to the upper bearing cups), and also sourced some new replacement ball bearings.

Replacement parts

These balls are 7.144mm in diameter (9/32") and widely available. Each relay has two oil seals inside. And they're different. The top seal is "double-lipped". As the name implies, it has a second lip that contacts the shaft within. This is to help provide an additional seal. I think, with some hunting, I could have sourced the seals from an oil seal supplier but, for convenience, I bought some from Der Franzose. Initially they sent me the wrong ones (more on that later too!), but I had no problems with an exchange.

So the top of the relays has a felt dust seal AND a double lipped oil seal. But even that combination didn't seem to stop water and mositure getting inside the relays.

At this point I was losing interest in the relays - or maybe gaining interest in the next jobs - the suspension arms. That would turn out to be another headache. You can read about that HERE.

I painted the relay parts when I painted the suspension arms last summer  - more than a year after I'd removed and dismantled them - but then shoved them in a box again for six months while I got on with other things. 

 

Painted parts

This year, with the car now coming together, I couldn't delay rebuilding the relays any longer and so recently dug all the parts out. I remembered disassembly being a bit of a puzzle (especially as I didn't follow the correct procedure), but re-assembly was very straightforward and it (and I) went by the book. Manual 518 to be precise.

All ready to go

Preparation

In my case, and having had so much trouble with that top nut, I wanted some options here. Before re-assembly I drilled and tapped a small hole in the top edge of the body - in line with where the nut would be. I planned to fit grub screws. The hole needs to be up near the edge of the casting - with a risk it cracks. The hole and screw size need to be big enough to provide some 'bite', but not so big that the hole gets too close to the edge of the casting.

I added a hole to fit a grub screw

 

Tapping the hole for the grub screw

With the bearing cups in mind, before you can fully reassemble the arm, it's advisable to make a simple tool to help with the bottom cup....This is shown in Operation Dx. 433-3. 

Tool 3904-T

This tool is used to push home the arm assembly - and most importantly the bottom bearing cup. I couldn't find any metal tube of quite the right dimension. It needs to sit just inside the inner diameter of the bodyso that it can press down on the face of the bearing cup. In the end I found a tatty piece of domestic plumbing waste pie that was about the right size. The cut out section slips over the cranked section of the arm.

My home made tool.

 

I applied a little grease to the inside face of the body to help with the refitting of parts. The bearing cups will be a very 'snug' fit. Before I began in earnest, I did a trial fit of the two metal bearing cups in the body - to make sure that when it came to the crunch, they were going to fit nicely. This was especially important for me as I had bought replacement cups. You don't want to end up forcing and jamming them.

With the holes tapped and a tool made, and with the fit of the cups tested, I was all set to go.

Relay arm parts

There was just one last thing. I familiarised myself with the job ahead and how all the parts should fit together. The scanned pdf diagrams available are quite blurry and don't show you what is inside very well. Here is a better quality scan of the relay arm parts. 

Relay arm parts and their orientation

In particular, it's worth noting the angles of the lips on the two seals (parts 5 and 8) and the orientation of the dished washer (part 2)

Top Bearing and Seal

The first step of reassembly was to fit the top oil seal in the body. This was pushed down to about the bottom of the machined area - about five or is inches down. Push it any further and it will simply fall inside the cast body. Look carefully at the lip as it's important to get the seal the right way round. The lip needs to to face up - towards the top of the relay.

New top oil seal in the relay body. Note the angle of the lip

Next the top bearing cup and it's balls were fitted. The top and bottom bearing cups look similar, but the top cup is the one with the smaller diameter inner hole. Two points. Firstly, you need to hold all the 14 balls in place on the cup with a generous amount of bearing grease for fitting.

Top bearing cup - ready to fit

Secondly, invert the body and fit the cup that way - it stops any balls falling into the body. Press the cup and ball assembly down (up) into the body until its resting against the oil seal. 

 

Oil seal, balls, and bearing cup

On top of the bearing cup, I placed the flexible (dished) washer. This needs to be fitted so that it's narrower end faces DOWN. If you fit it the other way up, it simply presses against the felt dust seal of the top nut and doesn't do it's job properly.

Next, the top nut was fitted. This should be fitted so that it's face is just below the top edge of the body (about 1mm or 2mm). If your oil seal was not pressed in far enough before, so the stack of seal, bearings and nut is above the rim  - don't worry. The seal will yield under the nut and move down to the appropriate level. If you pressed the oil seal in too far, again - don't worry. Just fit the nut to below the edge of the body. Then, from the other end, gently push the seal back so that it contacts  the balls.

The next job was to set up the relay arm for fitting. I polished up the bearing surfaces to try to compensate for some of the wear.

I polished the bearing surface on a wheel

Relay Arm Assembly

The diameter of the ball joint eye is greater than the dimension of the arm shaft, so these parts cannot be fitted after assembly. I first slipped the metal sealing cap over the shaft. Make sure you get it the right way round. Next was the bottom oil seal. Again - make sure it's the right way round: the lip of the bearing needs to be facing towards the splined end of the relay arm. Next I fitted the lower bearing cup. The dished face, that carries the balls, need to face towards the splined end of the arm. The metal cup and oil seal were slid out of the way towards the ball joint eye. I positioned the bearing cup at it's approximate position with the corresponding groove in the relay arm

On the relay body, and with the relay body upside down, check that the balls of the top joint (the ones fitted first) are still in place. Some of the balls may have fallen inwards - blocking the hole in the seal - but they can be gently coaxed back into position with a screwdriver blade or similar.

Now take the arm assembly and generously coat the ball groove, and thinner part of the shaft at the splined end, with grease. Do the next step over a bench or similar so that you can check no balls get pushed out during assembly.

 

Hold the cup on the arm over the balls in the groove to stop them falling out. Gently, and gradually, push the splined end of the arm down through the body. Do not go too far or the bearing cup on the arm will simply get pushed back out - with the risk the balls fall out. Carefully locate the bearing cup in the body.

Fitting the bottom bearing cup

 

So, as the splined end starts to emerge from the other end of the body, pay attention to the cup and balls on the relay arm. This is where you need to make sure the bearing cup fits straight into the body and does not get snagged. You want the arm to go through the body only at the pace that allows you to keep the cup on the arm, in contact with the balls on the arm. They both need to go back in together and this is where that tool gets used.

 

Placing the tool over the cranked arm, gently tap down on the tool, so that it presses on the cup. The cup will press against the bearings in the arm and gradually push the who lot through the body.

Home made tool for fitting the bottom bearing

 

To make sure you are applying pressure evenly on the bearing cup, you can carefully rotate the arm a little and then tap again. In fact it helps to rotate the arm anyway, just to make sure nothing is binding anywhere.

Eventually you will find that the arm is pushed fully home (i.e. the dished shoulder of the arm is pressed against the top bearings - which are held in place by the top cup and top nut). How will you know? Well, if the assembly has gone in as it should, you will be able to see and groove for the circlip at the cranked end of the arm. 

 

And the next step is to fit that circlip. I managed to snap one and promptly stick it through my finger. Now I know what having your ears pierced feels like.

Luckily they are a standard size and it was easy to replace. (The circlip - not the finger). If you find that not quite enough groove is exposed to fit the circlip, try backing the top nut off very slightly and then tapping the arm home again from the cranked end. With the circlip fitted, the oil seal can be pushed home and the metal sealing cap fitted.

It probably took more time for me to type the above, than it did to actually do the job. It just needed a bit of thought and preparation beforehand.

There is a particular torque for the top nut - but it's difficult to achieve without some kind of a nut tool that accepts a torque wrench. It's not very technical anyway: The nut is tightened to 6m.kg. I think this pushes everything together and removes any slack). The nut is then backed off until it is only just touching the dished washer. Finally the nut is re-tightened a third of a turn. this is expected to correspond to 2m.kg. However this assumes you are using a new dished washer and a new top nut.

Once you are happy, peen the edge of the nut over into the groove of the body. Or tighten your grub screw if you do as I did.

Grub screw in place

From what I can gather, the arm should be held 'securely' in the body: with the relay unit held on it side, the cranked end of the arm should not fall under gravity if the unit is shaken slightly - yet should move smoothly (more smoothly than it did perhaps?) when you push it with your finger. You might need to tighten or slacken the top nut slightly until you are happy with the pressure. 

My uncertainty over this is one of the reasons I chose to try using grub screws to secure the nut. A grub screw is probably not as secure as peening the nut edge over - but neither is it as destructive and I think that, if I needed to, the relay unit nut could be removed or re-adjusted again.

Alternatives

There are several alternatives to your own rebuild. If you're worried about your skills, or the quality and longevity, you can go for an upgrade. The arm is machined and re-profiled to take (three?) modern, sealed roller bearings. These kits can be bought for about £80 each - so temptingly cheap really. 

Upgraded relay arm kit. Note re-profiling. (photo credit: Der Franzose)

However there is another hurdle to be overcome before these can be used. As originally produced, the relay bodies are machined internally to accept bearing cups with a diameter of 46mm. It's the same for the oil seals. The new modern bearings have an outer diameter of 47mm. So before these arms can be used, you need to get the bodies machined to 47mm to suit. There was an error on Franzoses website and when I originally ordered replacement 46mm seals for my arms, 47mm seals turned up. Franzose gave me a no-quibble replacement, so I can't complain. 

This cheaper route also relies on you being able to re-use your top nut and not buggering up the threads. Having already tried the rebuild route that I followed, Peter eventually went down the path of re-profiled arms and new seals. he was lucky enough to find new top nuts. That's why he was able to offload various bits on me. He knows his way around a lathe but had to seek out someone else to machine his bodies for him.

If all of this sounds like too much hassle, it looks as though you can buy these upgraded arms with all the work done for about £200 each. You need to send back your old arms to have them overhauled for the next customer.

A re-profiled, and rebuilt arm (photo credit: Citrotech)

I probably spent about £70 in total rebuilding my arms. But there was effort, anxiety (and blood) along the way. What I've ended up with is better than what I had before, but almost certainly not as good as these rebuilt units. However it has left me free to waste my money on other things-DS.

My two arms have distinct casting marks and I will make sure I put them back on the sides they came from. I'll also make sure I put back all the relevant packing washers.