Losing rear differential oil on M1078 A1

[Zach_M1078A1]

M1078a1 Losing rear differential oil can’t find a leak CTIS appears to be functioning properly. Any ideas? Is it possible for the gear oil to be leaking into the CTIS somehow and into the tire while the CTIS still seems to be functioning and holding air?

 

[GeneralDisorder]

If there are any leaks in the hub seals it will pressurize the diff and can blow the oil out of the breather. The breather is connected to a hose that's routed up higher on the chassis so it doesn't get water inside it when fording. Follow the breather hose and see if the end is wet.

Hub seals are part of the annual service on these trucks. They are supposed to be replaced yearly in military service - likely not necessary to do them that often in civilian use but they definitely do fail - my right front CTIS port was wet with gear oil when I got my truck (CTIS had been removed).