Tight VC demonstration.

[syncrosimon]

This is my tight VC under test, the dub will not tick over in gear, the VC is too tight. Great for off roading though.

One rear wheel is jacked up, the front wheels are chocked by bricks, she should I believe tick over without wanting to move. no rear diff locks on, de-coupler coupled.

http://www.youtube.com/watch?v=Zzo8HZOoYAA" onclick="window.open(this.href);return false;

[syncrosimon]

Where as this one is loose, or certainly looser.

http://www.youtube.com/watch?v=zMqOebMnZKo" onclick="window.open(this.href);return false;

Simon.

[KarlT]

Good to see. Were they both tested cold or warm or hot? I've notice when hot its alot tighter.

[manxman]

to me they both seem similar, second on is using purpose made wheel chocks, far harder to climb than a brick and more surface area to resist the front wheels turning in the first place??

[syncrosimon]

On my dub I am using only just above tick over, the second vid he is using far more revs and still getting no where.

Yes it does tighten up even more when hot, doesnt happen now though with de-coupler.

[Simon Baxter]

I really don't think you need to go to that effort to check a VC, just driving them is fairly obvious if they are working or not.
Those tests are great if you buy a syncro, never had one and don't know what they are meant to be like but anyone who has any ownership or experience of them just know.
I can sort of see if they fail open but to me and what I have come across they generally get stiffer over time then fail open, you gotta be fairly daft if you own a van and just carry on driving it while the VC just gets stiffer and stiffer.
Nice you went to the effort though, great for new owners.

[..lee..]

looks like you may need a tow there.

[HarryMann]

I shall recheck mine tomorrow and see if I can get it videod... I know it's a bit tight but like it

[syncrosimon]

More the merrier Clive. Like Simon Baxter say's it may be useful for a static check of the VC, and for someone not familiar with a syncro, especially if the VC gradually goes loose. Never known with mine whether it is aggressive because it is knackered or because it is the military higher torque one. I had always wanted to do that test, and as Karl points out there is a difference between hot and cold VC's. Mine was tested cold, and is even more aggressive when hot, which points it towards being knackered, although I remember that even on my 27,000 mile 4 year old syncro it would tighten up after motorway driving, thats the joy of a de-coupler, take out the unnecessary strain.

[mattk918]

Been wanting to do some tests on mine, since I am one of those who hadn't driven a Syncro before buying one!! Went hunting for my trolley jack at the weekend and realised that it is still at my parents 150 miles away.... doh!

This subject of how tight is too tight is a tricky one though. Did 35 miles at 70mph last night then reversed on full lock up my packed gravel drive last night and it definitely hopped noticeably more than when i did it cold the day before. Question is at what point does this become a problem (cue smart answers along the line of "when your gearbox re-arranges itself into merely a container full of bits or spreads itself all over the road!!!)

[jebiga41]

have just replaced mine so will do the same test as a control when i get down to the folks house

[HarryMann]

Maybe don't jump to conclusions on full-lock... any VC will feel tight at full-lock, it's having to d=slipe quite a bit..
In fact, don't use full-lock unless you have to, just back off a little if it feels tight
When you need it, off-road with diff-locks in it'll be there and drag you up a steeper bank than you can imagine!

[mattk918]

Is there any other more scientific check that can be done? I was thinking something along the lines of fixing a thermocouple to the outside of the VC and plotting temp increase over time/speed etc..... i.e. over a certain temp in given conditions means fubar'd?

[HarryMann]

Yes, that would work.. but not on the diff-casing.
It would need to be on the VC casing itself, and thus not really tenable at a DIY workshop level of practice.

An easier solution would be to strain-gauge one of the diff mounts, to derive a torque-meter signal...

[dave friday]

in the syncro advertising it does say to avoid tight "u" turns as this will engage the viscous coupling and puts a lot of strain on the tyres !!.