I am currently rebuilding my 2nd GDU and have made some observations.
It seems that the forward gear fails regularly which causes catastrophic failures with the rest of the unit. The 3 damaged forward gears that I have, look to me that the surface of the tooth has pitting due to cavitation. This may be due to the loads seen, lack of oil on the surface or type of oil and surface temperature. I think the problem is lack of oil with only 1L of oil in the case I don't see how there is enough oil where it needs to be (at the gear faces). I imagine the oil being flung to the outside of the case due to the velocity of the gears and any oil in the "sump" would be moved away very quickly due to the crown wheel spinning past the drain. I think this also causes a lack of constant oil through the pump and cooler resulting in poor colling and high temperatures.
In my mind to increase longevity the GDU need more oil. The main problem with this is the breather location, as everyone says if you install too much oil it just comes out the breather.
So my solution block off the original breather.
Re-locate the return to the side fill point
Use the old return on the top as a breather into a catch can.
Fill GDU with more oil say 2-3L using a dip stick though the top new breather hole.
What do you think about this as an attempt to prolong the lift of the forward gear?
PS: One other thing that doesn't makes sense is the magnet on the fitting for the suction to the pump. See attached photo
All I can see it does is collect any debris and hold it right next to the crown wheel waiting to be stuck to a tooth and be forced through the rest of the gear set.
I'm going to remove the fitting and use a standard one so any debris and flow into the rock catcher or in my case Y strainer.
