I could use advice:

 

The Subaru r180 diff I am cleaning up seams to have something like plumbers putty on the bolts that hold the side covers on where the axles enter the case.

 

I’ve never seen this before. Is this to keep oil from leaking out from around those bolts?

 

Does anyone know what this stuff is and if I can get it at an auto parts store? I’d like to do this as correctly as I can.

 

Thanks.

False alarm!

I was able to find and download the FSM for the car this diff came from (2014 Subaru WRX STi). Here's the answer in case you were wondering…

• Apply liquid gasket to the bolts indicated by arrows, and tighten the side retainer bolt.
• Liquid gasket: THREE BOND 1110F (Part No. K0879Y0021), THREE BOND 1110B or equivalent
• Tightening torque: 10.5 N·m (1.1 kgf-m, 7.7 ft-lb)