VC "no engagement" failure

[PetenAli]

After using the Picos trip as a first real off road shake down of our Syncro it quickly became clear that 4WD was not engaging as it should. I think its quite a mark of these vehicles that we still managed to get just about everywhere everyone else did just with the help of the rear difflock and lower tyre pressures.

Since we got back I have carried out the test procedures as in the technical section on the Syncronauts site and we have a complete "no engagement" failure. Just to double check I did the procedures both cold and after a 20 mile trip to get things well warmed up. The result was emphatically no drive to the front wheels at all. (I did check that the decoupler was closing and the propshaft was turning!)

I have always been a bit suspicious of the VC - Vlux first noted that he thought there might be a problem when we went off roading on a Cornish mining site last October (2010). After that I took it back to where I got it but they assured me all was working well. I then assumed it was OK as we got everywhere we needed to in the snow last winter. I also changed the front diff oil last May and about 1.5 litres came out which smelt like normal gear oil.

I am going to have to get a new VC but I am wondering how the diff might have been affected if the oil has been polluted with VC fluid? The diff doesn't appear to get unduly hot. Would it be wise to get it checked over by Aiden if its out anyway?

I am going to put a post in the "Wanted" section but if anyone has a good spare VC for sale I'd be very interested.

Again, looking at the Syncronauts site and Jed's video, changing the VC seems fairly straightforward but any hints and tips would be gratefully received. I am going to remove the diff rather than try to change the VC with it in situ - I'll be mostly on my own and don't want to risk getting any crud in there.

Thanks very much,

Pete

[jebiga41]

You will be very lucky to get a good used VC and one thats too stiff will destroy your gearboxes Plus you have no way of testing it !!! I'm afraid you are going to have to get a refurb/exchange one Baxter does them

[jed the spread]

Hi Pete,

Just make sure you take the diff lock actuator off the diff before you drop the front diff as you could well break the lugs the hoses connect to on the actuator. My old VC had failed open like yours as did Lloydys when we did his in the video and none of ours had leaked any fluid into the gear oil. I found with both of ours that the VC would work for a very short time loosely when cold but as soon as it was under any kind of load it would fail open. Its not really a hard job to do and was the first real mechanical job I had ever done when I did mine with some help from a hung over Jake. I still havnt seen inside a Bentley or Haynes manual but I am quite lucky to call on friends and the good people on here if I mess things up to much

Good luck Jed

[PetenAli]

Thanks for both replies - I thought it likely that a decent second hand one would be out of the question (see my post in the "Wanted" section!!) but its always worth a try.

Thanks for the tip about the diff lock actuator Jed - breaking that would be a downer!

[jed the spread]

I thought it likely that a decent second hand one would be out of the question

The VC is a clutch, if its worn or doesnt work properly fit a new/recon one and get things working as they are supposed to like you would with a worn or malfunctioning clutch at the gear box end

jed

[PetenAli]

I thought it likely that a decent second hand one would be out of the question

The VC is a clutch, if its worn or doesnt work properly fit a new/recon one and get things working as they are supposed to like you would with a worn or malfunctioning clutch at the gear box end

jed

Good logic Jed - thanks. There's clearly no point in skimping on this one - do it once and do it right as the man said.

[syncropaddy]

If you are really stuck, I have a refurb VC in the shed with its paperwork. The likelyhood of a fluid leak is small so I wouldn't be too worried about the diff suffering. When ordering a replacement VC dont forget to add the cost of shipping the old core unit and shipping the new unit - they weigh quite a bit!

[Aidan]

you can check the pinion bearing yourself whilst changing the VC (grasp it like a joystick and try and push and pull it, any movement other than rotational is play) if there's play then get it fixed, if there isn't then unless it's leaking out of any of the seals or you find anything nasty on the drain plug magnet when you drain it it should be good to go, if the difflock isn't working or reluctant then you can sort that at the same time whilst it's out and do a visual check of the crown and pinion
generally failing open isn't a problem, the only issue is sometimes when it's been leaking a long time or the VC seals have been dragged through the lube holes there can be an issue with the internal spigot bearing, but that's easy to observe and check
if they go mega tight then there can be excess loads on the crown and pinion causing wear, generally manifests as a whine though

[PetenAli]

Thanks again for both replies.

Syncropaddy - I've quickly learnt that new / refurb is the only way to go so I'll probably go for Brickwerks as they are showing them in stock. Thanks for the offer though and for the advice.

Aidan - thanks for this advice. I'll give it a good check over when I get the diff out.

This site is soo helpful - you never feel that you are on your own.

Thanks again to all,

Pete