Syncro diff lock actuator lock seized but not.

[burnzdog]

Put a post on syncro forum but no joy... Thought I had a seized diff lock, actuator was broke so got a replacement. Turns out its not seized. Once I took out the sensor from above the diff it moved freely, I can move the plunger in and out with my hand. However it does not spring back like it's meant to. Where does this return spring action come from?

Sensor itself looks OK and mechinsm pushes in against spring but the diff definitely does like it when it's all the way in. Anyone experienced this?

[Aidan]

There is a spring inside the sleeve the difflock pin slides in; there is often corrosion at the point the pin seal sits at in the off position and so it may stick when operated - occasionally I have come across boxes where the spring is missing, it's rare but it does happen when stuff gets 'repaired', things get lost or omitted.
The difflock sleeve receives very slight splash lubrication but if the oil is highly carbonised then the yuck collects in the sleeve which doesn't help.
Sometimes people move the whole sleeve by trying to operate it (when trying to figure out what is not working) without the bracket and circlip fitted and the o ring seal for the sleeve gets cut by edge of the switch hole and the fragment of cut o ring falls into the switch hole in the sleeve and adds to the jamming issue too.
Bad news to get the difflock system fully operational and check the spring is present, ream the sleeve and polish the shaft so it's like new (change seal and o ring if necessary) and operates freely means taking the gearbox out, bellhousing off and stripping out the diflock parts from the inside so they can be worked on and then refitted
Do you have the 2mm hard aluminium spacer ring between the case and the tell-tell switch ? Have you tested the switch for continuity when deflected by a mm or so ?

[burnzdog]

Hi Aidan, just trying to digest what you are writing as I struggle a little with terminology..

If I slightly unscrew the switch it then allows me to push the plunger in, at a which point I can feel the plunger hitting the switch on its way in. I took the actuator bracket off so that I could get to the sensor to unscrew along with the little plate that surrounds plunger. When I took sensor off, the plunger moved freely in and out. What I'm finding is that when I screw the sensor back in the diff plunger gets to a point where I cannot push it on by hand. If I unscrew sensor slightly I can push it in and I can feel it pushing sensor back as it travels in.

The 2nd part of my question. Although I can freely push plunger in by hand I'm wondering how freely it needs to move in order to be confident that the actuator vac will work when I reassemble. I have seen videos on people pushing plunger in and it springing back out.

The 2mm spacer ring you talk of, do you mean on the thread of the sensor switch? If so then yes.

[burnzdog]

Here is a short video of the plunger pushed in by hand without sensor installed.
https://photos.app.goo.gl/tMwMz48f1anTf6FT8

[silverbullet]

Its a switch for the warning light. There is no sensor. Makes for confusing reading.

[Aidan]

All is clear now, the sleeve is moving in and out of the case, not the pin which is seized solid, so when the tell-tell switch is fitted it is preventing the sleeve moving (the sleeve should not move, only the pin inside the sleeve should move, if the plate and vacuum unit bracket are fitted with the circlip fitted then you would not currently be able to push the combined pin and sleeve in).
Sorry but you are unlikely to free up the pin in the sleeve, but you can try; fit the external plate and the bracket and the circlip, pop some gear oil in the tell-tell switch hole and then try to w4nk the pin in and out using whatever you can use to pry the pin out if it goes in and sticks, repeatedly till you can push it in with your little finger and it will pop back out under the internal spring pressure, then you can fit the switch and vacuum unit and all should work - but I'd be surprised if you can free it up

[burnzdog]

I literally just realised this as the circlip made no sense. Oh joy, another impossible job that will cost 1000s.

Thanks for help.

[silverbullet]

After refitting the plate and bracket and dribbling some oil down the switch hole, carefully and gently warm the sleeve end with a gas torch. The sleeve will expand more than the pin which will help it get moving.
Use appropriate heat sheilding such as a plumber's mat and be mindful of the fuel tank and anything else plastic or rubber.
Keep a fire extinguisher to hand.

Or...drop the transmission and get at it in the open air.

[burnzdog]

Thanks i will give that a go

[Aidan]

its probably 6 hours to remove the gearbox, remove the bellhousing, remove roll-pin internally, strip out difflock parts, sort shaft and sleeve etc.. and reassemble and then refit gearbox, a bit longer if you don't have access to a lift and are doing it on axle stands on the floor, so £500 max inc the vat at a competent garage
If you are visiting mid - north- Wales on holiday then book it in with Brian and the team at the garage 200 yards from me, Station Works Garage, Llanfyllin, 01691 649 649 - Thursday morning is market day in Llanfyllin, plenty of nice countryside, a café, several pubs, the Workhouse , chippy etc. here so stuff to do while van is sorted, they are also a mot garage. You can camp here night before garage for early start......

[burnzdog]

3 hours later and a little bit of persistence seem to have worked.

https://photos.app.goo.gl/KteDE168Fh4JqdNV9

I will consider putting this back together now, does anyone know how far the pin head of the actuator should go into the plunger? I ask becuase I had to drill the old one out as the top had snapped off and I had to drill it, but I do think I have drilled enough but it's difficult to gauge.

[silverbullet]

It should go in until the neck of the red silicone boot touches the rod. The rod is also case hardened so you shouldn't be able to drill it.

[Aidan]

3 hours later and a little bit of persistence seem to have worked.

https://photos.app.goo.gl/KteDE168Fh4JqdNV9

I will consider putting this back together now, does anyone know how far the pin head of the actuator should go into the plunger? I ask becuase I had to drill the old one out as the top had snapped off and I had to drill it, but I do think I have drilled enough but it's difficult to gauge.

well done

12.5mm ish to the bottom of the hole for the vacuum unit