Big T,
Same thing was happening on my '37 Chevy half ton project when I got it. That is gear oil from the differential/axle. As you probably know, the rear axle bearings are lubricated by the differential gear oil that sloshes down the axle tube. The rear axle housing rotates on the brackets that hold the axle to the springs, that is why you have a grease fitting, seen in your first picture. Those brackets have an internal slot machined in them where a spacer rides, to keep the axle from sliding side to side. That spacer is held in place to the axle housing by two large rivets, the heads of which are inside the axle tube. As the assembly wears, it deforms the rivets and/or elongates the holes in the axle tube allowing gear oil to seep onto the springs.
To fix that you would have to dismount the axle and remove the axle shafts. Using a piece of pipe as an anvil, placed into the axle housing from the side, we reset the rivets by hammering on the spacer. That tightened things up and I recall using a sealant around the spacers in addition. So far so good but I haven't put much mileage on the project yet.
It shouldn't hurt anything to leave it be, just put a pan underneath and keep an eye on the gear oil level. You can fix it later when need to do some other repair involving the rear axle.
Kent
Last edited by Lightholder's Dad; 07/10/2017 4:02 PM.
