The sensor is walking out of this 9.25 and that results in gear oil everywhere.

I merely identified the smoking gun last night and haven't actually touched it.....but I'm drawing a blank on what retains it and how it would have done this??

I'll be laying hands on it this morning but figured if the board had input it can only help me....

This is the later style if it matters, circa 2000+

 

Should be a bolt that holds it in place.

 

The cylinder looking thing behind the sensor is a bolt. The body must've broke off. Need to open up the diff and see if anything inside caused it, e.g. blown gears.

 

Should look like this:

 

Ok, well the mystery continues....this thing is losing gear oil but I'm not sure exactly how.

You can see the oil in the pics above, it's all over the top of the pig, LH shock and primarily LH axle tube. It's also up on the rubber brake line not quite to the frame.

At first I thought *maybe* the LH shock blew (new Rancho) but I've never seen a blown shock produce this much oil and it wouldn't explain the rear being exactly a quart low, just freshly filled this summer.

Wheel seals? Well, maybe but I'm not seeing any gear oil coming out of drums and doesn't explain oil all over pig.

Axle tube press fit on LH side? Eh, maybe....but that'd be a helluva lot of pressure to make it up on the flexible brake hose and all over LH shock..

Pinion seal? My instinct says it's been oozing for a long time but I've never seen a failed seal at the snout send oil so high and only favor the LH side

Tone ring sensor? So I thought but it WAS fully seated and the o-ring looks a little tired but overall "good". Is it possible to blow a quart out of a properly seated tone ring sensor? Not terribly likely but.....

MAYBE....if the breather were plugged? Breather appeared good and the gear oil definitely wasn't being pumped up the breather as the top several inches of the hose was clean outside and inside. The factory baffle cap showed no signs of gear oil.

I keep going back to the pics above where the sensor appears washed clean at its base and it would appear the not-atypical metallic goo was getting pushed out.

For now I'm theorizing -- perhaps poorly -- that the tiny factory breather was somehow clogged/pinched off. Maybe this forced gear oil out the sensor. Still, it's a lot of gear oil to get past a small space. I've re-worked the breather with a much larger hose and cleaned everything up. Now to see if it reappears and where. I tried idling on the lift in 1 for a half hour last night and nothing

 

Oh and for the file of useless trivia: the factory breather threaded into the LH tube is 7/16-20

I thru-drilled a 7/16-20 bolt 1/4", turned the hex head round and did some rudimentary grooves with my cutting tool to give a hose something to grip onto.

The factory barbed fitting has a TINY ID....maybe 1/8"?

All the problems seemed to start with the really cold CO weather, so I'm still thinking heating/cooling, expansion/contraction.

 

Go for a drive, park on a flat spot, and crawl under there right as you get back. See if you see fluid dripping anywhere. Pinion seal seems the most likely to me, as it will spray fluid out......

 

To me this looks like someone tried to remove it with vice grips after they broke the tab off.

 

Ok it certainly appears to be the sensor, I cleaned everything up and it's pretty obvious.

I actually think it's coming from "further up" the sensor and running down, rather than at the base with the o-ring

 

Here's the thing: as you can see this sensor has the plug 180 (or inline with) the bolt hole. It does also swivel, which I figured was normal-- it's smooth and doesn't feel "broken". It was like this back in May when I installed the rear end, so the swiveling is not new but the leak is.

The aftermarket sensors I've seen -- and I fondled one in person at O'Reilly yesterday in the course of my research -- are at a right angle such that the plug faces the pass side, and it did NOT swivel.

How does one rectify a side-facing plug with the sheetmetal guard seen here? I can simply eliminate the shield and/or modify it, but is that SOP?? Why are aftermarket sensors 90 degrees to my example?



Plug swivels within the confines of the shield....