Spinning backwheels in 4-WD

Oki. Soo the vaccum system must be working in order to send the "go" signal to computor and to get the a steady 4WD indication on the panel. But the front hubs are stuck and does not commect to the shaft!?

Yes that is a possibility. You should be able to hear if one hub isn't engaging.

Its a clear sound from one front hub but not so from the other. Would it make the car 3WD or do this cancel the bouth front wheels?

You need both hubs to lock to get drive to either front wheel.

If one hub goes click= 4wd engages  and clack=4wd disengages, but not the other then there is probably a blockage in the pipes.


One sure fire way to block the ports in the hub is to replace the wheelbearing. Over enthusiastic greasing blocks the thin port in the hub with grease. (Both ports have to be clear, as it is air going in that pushes the hub when vacuum is applied to the other port)

get hold of a 100ml syringe of similar and use it to suck air out of the spigots on the hub one at a time, You should be able to move the hub and hear it click and clack. If you can, investigate the pipes, if you can't, remove the black outer hub, and then you can try blowing the ports clear. (if you don't remove the hub, the air has nowhere to go)

Then there is the possibility that someone crossed the pipes over. This one is trial & error until the hub locks when you select 4wd with the engine running. (The system only supplies vacuum for a few seconds to move the hub so you have to keep going from 2wd to 4wd every time you test it)

 

Thanks for the explanation. I don get this fully:

"If one hub goes click= 4wd engages and clack=4wd disengages, but not the other then there is probably a blockage in the pipes."

What will be the effekt on the car if only one hub "click"? I suspect that is what happens accoring to how it sounds.