SoCal Trail Damage to Rear Diff/3rd member - leaking

Went down to around Anza Borrego this last weekend and had a blast! The only hiccup is a bit of rock damage on the diff, but this is good for dad lore.

My buddy Alex went up before I did (2020 Taco DCSB 4wd) and got there during the day, found a spot, and was waiting for me to arrive. I got there late at night and once I got to the trail, I gave him a call and let him know I'd be there soon. He started walking down to meet me.

Turns out the river wash was luckily dry, but still had long stretches of softer sand that I had not anticipated. I had just got off a 7-hour drive, and I sadly wasn't in the mood to stop, air down, and go slowly through a trail I hadn't been on before. I foolishly decided to just give it beans and let momentum get me through the soft stuff- which ended up being the stupid decision that led to this situation. Slow is pro and I chose against it.

Going at a decent speed, I made a turn and immediately saw a big pyramid-shaped rock sticking out of the middle of the riverbed/trail. Without enough time to react - BOOM - the rock hits the 3rd member almost perfectly down the center. Alex gives me a call, "Was that you just now I heard????" - He heard the impact from like 1/2 mile away!

Checked underneath and saw the drip, decided I might as well finish the last leg and get to the campsite.

Once at the campsite, got under the truck and saw this:

Missed the bolt by just 1mm but still broke the seal on the gasket between the 3rd member and differential housing. We couldn't do anything that night we threw a bowl underneath and went to bed.

Woke up bright and early at 6am, took Alex's Taco and drove to Brawley O'Reillys to buy a bunch of Black RTV, Brake Clean, some wire brushes,

$29 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 Gear Oil, and a pump. Got back to camp around 8:30 and got to work. Cleaned up the area, layed down some RTV and let that set. Spoiler: it didn't help.

Over the next 5 hours or so, I would add a small layer of RTV, it would hold the leak, and then seemingly as soon as I looked away, it would burst a bubble of oil through the RTV and continue to leak.

Lost maybe 1/2 a quart over the 1st 24 hours, but we only needed to top the diff off once.
In either case, it was time to go home and call it a day.

The drive home was supposed to be 3 hours but took 7 hours. This is because every 20-40 miles I would stop and check the rear diff leak. At first, it was dripping pretty fast, but by the end of the drive, it seemed to slow down I think. Got home okay and put a bowl underneath.

It's now been a few days and the leak hasn't stopped, obviously, but it's a slow drip leak. It won't stop completely until the diff is properly resealed. For now, I'll keep checking, topping off, and keeping a bowl under it, but the full fix will happen in a week or so unless something else goes wrong.

The plan is to chock the front wheels, raise the rear axle, drain diff, disconnect driveshaft from 3rd member, remove wheels, drum brakes, axles, then finally remove the diff, clean up the mating surfaces, fresh RTV, reassemble, torque, wait to cure, fill, and be back to business.

If anyone has any experience, tips, or warnings, I'd love to hear it because it'll be my first time resealing a diff. I'm pretty handy and will have help, but it doesn't hurt to test the waters and get more info!

Cheers!

 

Are the bolt tight?
At this point you're home.
But tightening the bolts (nuts) might have slowed it down some.

 

Forgot to mention that! Yeah, I tightened what bolts I could but I didn't want to strip any nuts so it was just a slight nudge. Maybe it helped maybe it didn't, not too sure because it's still leaking. Leak is progressing though so it's looking like I gotta borrow the family Camry for a week until I get the time to do this. Been refilling about 1/2 quart a day since it happened and its honestly just annoying having to check often and top it off.

 

I don’t know if anything else is compromised.

but either way sealant is not gonna seal if there is gear oil on it. Diffs are sealed putting them together after they are cleaned and dry.

 

I never followed up so here's a quick wrap up update.

Got everything repaired in one day, a couple months ago now. While I did pop the seal when I hit the diff, none of the studs were affected nor were the two mating surfaces.

Chocked the truck, took off wheels, undid driveshaft bolts, unbolted axles and diff. Pulled axles to the side, pulled out diff. Hardest part of this was just keeping the axles out of the diff but a buddy helped with this. With the diff pulled. we used a fine wire wheel to clean the mating surfaces and housing. On the diff, the original paper gasket had to be cleaned away first. I used a pocket knife and carefully picked at it without etching the surface. With the paper gasket gone, we used the wire wheel to clean the surfaces to a nice shine. Applied a Bead of RTV Black to the housing and fit the diff back in place. Torqued everything and reassembled, waited 24 hours to cure, and refilled diff. Drives like nothing ever happened.

The take away is it wasn't too bad to fix and only took like 3 hours with a buddy. No more leaky diff. The problem is I have no mechanical sympathy for this vehicle and will probably do it again.