Vacumm Hubs Just For a Change

Last year I thought I had a problem with the front hubs, my back wheels lost grip, so put it in 4WD and it didn’t seem much better. A few days after I jacked up the front and tested the vac hubs, both worked correctly.

All has been great until Saturday, it was cold and there was ice/snow, the back wheels spun when in reverse up a steep drive. I put it into 4WD and tried again, it was better, but I still felt the back wheels slip, I am pretty sure the front didn’t.

Both times the green light came on, but then it comes from pressure not hub position, I think?

Is it possible that that one or both hubs work sometimes and not others? If only one hub was engaging and not the other, would you still get good drive from that wheel or would it cause problems with the diff?

You need both hubs to engage to see useful drive otherwise you will just rotate the diff centre.

Thanks Lambert, that explains the Eddie's (original poster) experience, one drive shaft turned but with no power, the second not at all.

So if one hub vac line is blocked, you get a steady green light, but no 4WD. I suppose you could have one hub sticking in cold weather as well?

I might jack mine at the weekend and check operation.

I used the earth conductor from some twin and earth cable. If you have a compressor then the small air guns you get to use with them would do the job.

Mine had no light at all from pushing the 4x4 button. At first when it failed a blink after 3-4 sec, but later in the week nothing.
Now with only minus 2 it is working fine again.
I suspect the actuator was frozen. I had been driving in deep powder snow and minus 15 so most likely packed underneath with snow.

If the actuator engage but the hubs not, the light will flash?
Or could it be the vacuum sensor at the intake manifold?
Or does it still flash the light if that one is out?

Just jacked the front of my Jimny and neither vac hubs are locking.

I get a solid green light on the dash and the transfer box is working as it locks the front drive shaft. The solenoids are clicking so my guess is it is something common, perhaps aa blocked pipe where it is common?

Apart from taking the vac hoses off each hub is there an easy way to tell if the vacuum is working or not, or possibly blow out both lines from the solenoid?

Robin