Good technical Question

[lloydy]

I've asked this on saturday but don't quite remember the answer
If van is stuck and has one rear wheel in the air and that wheel spins up, and diff locks are not working, am i right in thinking power doesn't go to the front. This seemed to happen to me. But on the road if i put the rear wheels on ice and made them loose traction it sure felt like the front wheels got power.
I'm sure this is correct, and is the reason we have rear diff locks. [sorry jed, i know you told me but my brain only holds a certain amount of info ]

[ringo]

If the VC is working you should get traction on the front.

Jed will be along soon to show you a video

Ringo

[jed the spread]

2.27 in and you will see a failed open VC, http://www.youtube.com/watch?v=g6Yn73c8Wsc

jed

[jed the spread]

If the VC is working you should get traction on the front.

Jed will be along soon to show you a video

Ringo

You know me to well

jed

[lloydy]

2.27 in and you will see a failed open VC, http://www.youtube.com/watch?v=g6Yn73c8Wsc

jed

You see thats my memory! I was thinking that both rear wheels had to be spinning to make the VC work, maybe i had a front wheel spinning as well?
As it sure seemed to me i was getting power to the front earlier

[jed the spread]

It will spin for abit then that should activate the VC, as I understand it. If it just spins and you dont move its because it is failed open I guess.(obviously without the rear diff lock on).

jed

[lloydy]

Bad news then
Just followed a VC test on youtube [syncrosimon among others] Of jacking up one rear wheel and chocking the front. Rear wheel spun and front wheels didn't engage on tick over in crawler gear. So new VC will have to be purchased

[ringo]

Bad news then
Just followed a VC test on youtube [syncrosimon among others] Of jacking up one rear wheel and chocking the front. Rear wheel spun and front wheels didn't engage on tick over in crawler gear. So new VC will have to be purchased

That will be the money pit then

I'd be getting a second opinion mind!

Ringo

[..lee..]

i test mine on the roller brake tester in work. if you drop the rear wheels in the rollers and try and drive out you should be able to rotate the rear wheels slightly but once they start to turn you should feel the fronts start to pull you out. no rear wheel slip before pull out and the vc is tight, too much rear wheel slip before pull out and the vc is inop.

[Aidan]

i test mine on the roller brake tester in work. if you drop the rear wheels in the rollers and try and drive out you should be able to rotate the rear wheels slightly but once they start to turn you should feel the fronts start to pull you out. no rear wheel slip before pull out and the vc is tight, too much rear wheel slip before pull out and the vc is inop.

if you do this test with the engine and running gear properly warmed up slip the clutch in G gear with no accelerator it should sit on the ramp with the rear wheels turning and fronts not with the vc dumping the power as soon as you give it revs it should pull off the ramp, that would be a very good vc and try it half a dozen times if it does it once then it's a pass, if it tries to pull off every time vc is too tight, if it doesn't try to pull off then VC has failed open and you'll find the front diff oil is contaminated with silicon and stinks

as a quick test raise one front wheel off the ground vehicle in neutral prop on and try and turn it by hand, if vc good you will just be able to rotate it very slowly, if failed open then it will turn easily and if you can't turn it at all it's too tight

[lloydy]

i test mine on the roller brake tester in work. if you drop the rear wheels in the rollers and try and drive out you should be able to rotate the rear wheels slightly but once they start to turn you should feel the fronts start to pull you out. no rear wheel slip before pull out and the vc is tight, too much rear wheel slip before pull out and the vc is inop.

Would that be the same as jacking one rear wheel off the ground?
as per these
http://www.youtube.com/watch?v=zMqOebMnZKo
http://www.youtube.com/watch?v=Zzo8HZOo ... re=related

[lloydy]

a

s a quick test raise one front wheel off the ground vehicle in neutral prop on and try and turn it by hand, if vc good you will just be able to rotate it very slowly, if failed open then it will turn easily and if you can't turn it at all it's too tight

Thanks aidan, just tried that. Wheel is hard to turn, does move but you have to put effort in [stiff in other words]
So thats a good sign. So why if i jack one wheel off the ground, put it in g gear and rev it, it doesn't seem to move [front wheels chocked with brick]
Couple of times it kinda felt like it was going to do something [almost forward motion, like nudging].
Seems good though if front wheel is stiff.
Will this test only work a good drive around? As i did it on my drive from cold
Cheers, Lloyd

[Aidan]

vc is stiff when stone cold then becomes less stiff as it gets to normal operating temp and behaves as it should, so then only when there's slippage between the front and rear do the temps rise inside the VC and the state change from open to closed, so yes the test needs to be on a fully warmed up by driving system;

[lloydy]

so when its cold i.e. On mh drive the test won't work? VC wont engage?. Good sign the front wheel is stiff though? Will warm it up good tomorrow and try again. Cheers for the info

[syncropaddy]

I always thought that you had to jack both rear wheels off the ground to do a VC test. Lifting one rear wheel will let it spin out.