Are they leaking out the cap, as shown in pic 3? The cap in the pic looks bent? Those caps are just press fit and they hold the oil in each side, if they are bent and leaking bad, you are going to need new caps, properly pressed in. I found the screw on cap to a full sized oxygen bottle (from oxy/acet welder) is a perfect fit to hammer the cap in, in an emergency
I have had them litterally fall out unnoticed, dirt got in and gears had to be replaced. So be very careful with them. Inspect them carefully. They should not leak!! I suppose everyone should check theirs periodically as I have had 'em fall out a couple times. NOT a good set up at all!
Good luck !
. . tug
PS: By the way, they are called the "Final Drive Spindle CAP".