Air bubbles in transfer case oil

[Bris31]

I would like to know on behalf of my friend's FG84 2010 presence of air bubbles in transfer case oil, otherwise oil is absolutely clear when bubbles clears in about an hour. Gear box oil have no air bubbles and clear. Oils levels were being investigated because of a presumably shuddering noise coming from gear box or drivetrain when in 4wd at about 30km/hr speed only briefly.
Oils were changed about 3000km ago.
What are the possible causes, how serious it is, solution etc. We are in the outback on CSR and about 700km from any diesel mechanic workshop.
Thanks in advance.

 

[Aussie Iron]

Air bubbles in gearbox oil would be fairly normal just after it has been driven. It is being stirred up just by the actions of the gears going round. Time it takes to settle Etc. is in all the additives in the oil (antifoaming and all).

To me it sounds like you are getting gear train "windup". Reasons can be difference in tyre diameters (difference in tyre pressure front to rear). Load of Canter even effects this (front to rear) . Rear limited slip binding (the additive in the oil may have broken down).

Okay, Drive Canter till noise is heard - stop - jack up one rear wheel - see if it spins by itself as it is leaving the ground (unloading itself). No, drive again till you hear noise. now try front wheel. If it is getting windup - change tyre pressures. Front - rear till you can solve it. Even sometimes it may be side to side.

"Torsen" in the front sometimes can bind (this is gear bind (maybe not the right word) - it is how it works) at low speed just by what it is. Oil quality can have an effect here.

Problem - yes (maybe), if it was mine, I would drive it and investigating what is causing it.
Dan.

 

[Wazak]

Does the either axle have a Limited slip diff? If so the wrong oil may have been used, you need a good quality LSD oil not just normal gear oil.