You have a inner seal leak. You will need a few tools to repair. 1 -3 inch socket, 1- 1/12 socket, Jack, a few 1/2 sockets 1- slide hammer, 1 set of rear axle puller tools, 1 inner seal, inner grease seal, outer grease seal, 1 boot if needed, tube of silicon, 1 wheel cylinder rebuild kit, just in case of leak. A box of shop towels, A cardboard box with plastic bag inside to catch the goo. 2 tubs of grease.
Jack truck, remove tire, hub nuts, lock ring, outer axle nut inner Axle nut, grease seal, pull brake drum off Be careful not to damage threads on hub. Remove upper king pin bolts and shield. Place box under hub Unscrew boot clamps, . Remove return spring, remove 10 nuts and retainer ring, Place brake backing plate above axle, I used a bungee cord to hold in place,. tap hub and pull off. Remove shaft by pulling it out, clean and inspect for any damage. Clean all oil and grease out of hub, Put bearing puller tool behind seal and retainer ring, that big silver washer. Screw in slide hammer, tighten, and whack away. Knock out the old seal, clean retainer, Make sure the flat side of seal is facing out to the tire, Silicon the seal into the retainer, Trust me it will leak if you don't, not that i found that out the hard way. Silicon the retainer ring that goes into the Axle housing and Install. Make sure it seats in axle. Grease inner lip of the new seal. pack some grease in front of the retainer so you have some grease between the thrust washer and retainer. install the shaft, pack the hub with grease, Clean and silicon hub, Install king pin with 2 bolts to hold it togrther, Inner boot clamp. Outer clamp, boot sheild, Grease king pin zerk Hub, backing plate make sure its strate up and down and brake shoes are left to right evenly, retainer ring , washers, nuts, tork to specs, Spring, new inner grease seal, repack bearings, install drum outer bearing, seal, washer,nut tork to 50 back off 1/8th other nut tork to 100, lock washer bend tab, hub cover tork 30, tire check oil in axle, clean vent, and drive.