CHANGE OIL To change oil remove 3/8-in plug on bottom of gear box. Use a 5/32-in hex head wrench, FSN 5120-198-5392. It's in both No. 1 and No. 2 Common Tool Kits. (it's Key Set, Socket Head Screw). After draining, replace plug. To add new oil, remove the 3/8-in plug on top front of gear box (you can use the some hex head wrench). Add 26 cc or approximately 9/10 ounce of MIL-L-7870 Lubricating Oil, General Purpose, Low Temperature. a~II