Mid differential leaking on Kenworth t680

They're just installed with RTV as a gasket. Bolts could have not been torqued correctly or the RTV wasn't applied to the surface properly. Very tiny possibility there's a casting defect on the mating surfaces but I doubt it.

This is why manufacturers provide warranty, sometimes little things get missed during assembly. Thankfully that job isn't a major one. Driveline off, axles out, slide the diff assembly out, clean the mounting surfaces, new sealant and reassemble. Shouldn't take more than a couple hours.

 

The bolt in the second picture looks like it loosened and backed out a couple threads. Or was never tightened up from factory to begin with. Get them tight they are what is holding in the gear set.

 

Kinda looks like it’s probably leaking where the chunk mates to the housing or possibly one of the bolts…are they tight? Just asking because I’ve seen them loose and simply tightening them will solve the problem for a long time. Or maybe the leak is up higher and just running down

 

Put a wrench on them. If that one is cross threaded and not all the way in it will allow oil to leak past it and you will not be able to turn it by just your fingers. Needs around 95-100 ft lbs of torque.

 

We reseal a lot of these under warranty. Bolts are tight, just not enough RTV or not cleaned well when assembled.