I think they're like a rosette type of weld. They drill a hole put the material they want to attach then fill the hole with a welder. makes for a clean job. Other wise you would have a weld bead around the contact point where the shaft and diff meet. just my opinion.
Every jeep diff I have worked on looks like that. The weld inside will be very clean once you clean the slag and rust out. Clean very well before you prime and paint, it will be fine.
Dan Schultz
MD20035 9/1952
MC70324 dod 6/52
GPW 14944 dod 4/10/42
K38 Linemans Trailer 4/43
M100 Trailer 01177488 dod 8/51
The location of the weld is normal from production. The weld quality varied back then and that particular weld on your jeep is porous. My M38 also has a less than perfect weld. You won't have a problem with that axle housing. After many years my weld shows signs of weeping a little rust out of the porous weld. If you want to be meticulous spend time brush priming.
Another question on the rear differential back plate. The bottom hole has damaged threads and I can't get the bolt to tighten. I have never tried to Heli-Coil anything, but am pretty handy... so am I better off learning on this or just taking the rear axle into the local machine shop and have them do it?
I think it is something you could do. Problem is the cost. When you buy a a Heli Coil kit, you get just one size and pretty pricey, $40-50 in my area. It probably wouldn't cost that much more to have a shop do it, then you would also know it's right.
Dan
Dan Schultz
MD20035 9/1952
MC70324 dod 6/52
GPW 14944 dod 4/10/42
K38 Linemans Trailer 4/43
M100 Trailer 01177488 dod 8/51