Rear differential leak following exhaust fix

[vanwagoncowboy]

Last night (9/17/21) my exhaust pipe broke where it was welded and I had to rig it back together with a hose clamp in order to get it home (12 miles from where I was). This morning (9/18/21), I got up early and found a muffler shop that was able to see my van that day. They barely had it a couple hours before calling to let me know they welded it back and I was good to come pick it up. I went to the shop and picked it up without any other issues mentioned. When I got into the vehicle and started it, I heard a small pop right as I took my foot off the clutch and lurched forward to pull out of the parking spot. I had never heard that noise before so it caught my attention but I was not sure what it was. Later in the day I left my house and as I was reversing out of my spot I heard the pop again. It was almost as if I had to press slightly more than usual on the gas to engage in reverse whereby the van made the pop but then sounded and reversed as it normally does. I questioned what it could be but was still not sure. Fast forward a few hours later and as I was leaving the place that I had driven to I went to reverse out of the parking spot and the same pop happened. I got home and slid under the van to inspect the underside and sure enough, I saw that my rear differential was seeping. My question being is there anything that the mechanics could have done that would've caused this issue? I was hoping to get some feedback from more experienced members that may be able to give an educated guess as to how this happened so suddenly. Is it a coincidence or was there something the mechanics did when putting my van on the lift or did they have to dissemble the driveshaft to weld the break??? Thank you for any thoughts you may be able to contribute.

[Burntboot]

Its not an entirely uncommon occurrence, but it isn't the shops fault.

Most times, this situation is caused by a seized rear U-joint.
It doesn't cause a lot of obvious issues to the driver, more like easy to ignore stuff, squeaks, vibrations...
Then it gets put on a hoist, the suspension drops and the angle of the rear joint changes and because its already seized, when put back on the ground it wont return to its previously happy position.
The vibration caused by the stiff joint is enough to wipe out the pinion seal in short order.
(It had likely already started prior to being hoisted, now its just more obvious)
Ignoring this problem will result in needing a new diff, so best to get it sorted sooner than later.

There are at least 2 threads out there about this, early vans had replaceable joints, later ones are staked and considered non-serviceable.
The easy solution is a new shaft or have yours rebuilt by someone who actually knows what their doing (many don't but claim to)

[vanwagoncowboy]

Thank you very much for your reply BurnBoot. I was basically fishing for your reply without trying to ask any leading questions. I thought the issue somehow came about from the way that the mechanics may have driven it on the lift or it just going on a lift in general. I have heavily researched all forum posts under driveshaft and rear diff and will be looking into contacting and purchasing a Powertrain driveshaft this week along with new seals.

[Burntboot]

No worries, glad to help.

I'd pop the driveshaft off the diff (please mark it first) and articulate it thru its motion, just to be sure.
You might even get away with a visual inspection, if you see orange dust around the cap seals on the U-joint, that would be also definitive.