Diff Oil on Wheel Speed Sensor Normal?

2007 Tacoma PreRunner TRD Off-Road, 4x2, 207,000 miles.

ABS/Brake light illuminated. Took to Nashville Toyota where they plugged in a scan tool, which showed a problem with LH rear wheel speed sensor.

Their estimate was close to $500, so I ordered 2 new eBay wheel speed sensors for $11.

I just pulled the LH rear wheel speed sensor and there’s diff oil on it. Just for the sake of experimentation, I wiped it off, re-installed, and went for a short drive. ABS/Brake lights still on. Came back, pulled it back out, more diff oil on it.

My question is this: Is it normal to have diff oil on the speed sensor, or is this an indication of a failed axle seal?

 

Oh well. Popped in the new $5 eBay sensor and the ABS/Brake lights blinked out after I drove about 100 feet.

Hopefully the diff oil on the sensors is just some minor leakage, and my axle seals will live for a long time to come.

I did pull the other side sensor and it had a slight water/oil emulsion on it as well.

 

Yeah you shouldn’t have any oil there and it can contaminate the brakes. Fix it before they puke oil all over everything. It’s not that hard of a job and parts are cheap as long as the brakes already aren’t contaminated

 

OP, I don't want to be that guy but I'm afraid you are in for a little more than an issue with sensors here.
What is likely going on is the axle seal on the side of the differential has gone bad and allowing gear oil to pass the seal and end up in the wheel bearing. Things often snowball from this leak as the gear oil will wash out the grease in the wheel bearing, ruining it, and then continue through the bearing and drip on the brake shoes, ruining them.
If this were mine, at that mileage I would replace the axle seals at minimum on both sides, and probably do both rear wheel bearings. If you get lucky you may be able to save shoes.

 

Yeah, you’re probably right. I probably need to start looking into going ahead and getting ready to do that job. Just hate to fix what ain’t broke (yet).

 

I fully understand but it is broke and unless addressed soon the problems and costs will just ratchet up from here. Sorry.

 

Oh, no need to apologize! I suspected the seals were leaking as soon as I pulled the sensor and saw diff oil on it. I pulled the right side just for comparison and it didn’t seem as bad... But, I have been wondering how long some of the components like this would last. The truck has required very little maintenance - so far the biggest things I’ve had to do have been u-joints (the rear one started squeaking at around 80K, so I went ahead and replaced all 3), serpentine belt idler pulleys, and that’s about it. No major component failures in 207K.

But, I know a couple of other guys with Toyotas - one with a previous-gen Tacoma and one with a current Tundra, and both of them have had to replace these seals.

So, it’s not a surprise.

The cheap/lazy part of me just asks, “What’s the worst that could happen if I just allow the seals to completely fail until I see oil leaking out?” If I go ahead with the job now, the only thing I’d potentially be saving would be the brake shoes, right? It could be a long time before one or both of the seals start leaking bad enough that oil gets into the drums.

 

Not a good philosophy though. In my experience, when they decide to go they go. Oil everywhere and total mess! If you fix it under a controlled situation you can change them without any oil loss. Maybe it’s already time for new shoes for you but if your drums are good you don’t want oil all over them.

 

Yeah, it hasn’t been that long ago that it had a rear brake job. And, as you know, they don’t require one often. I don’t know the exact mileage, but I think I had it done less than 2 years ago. So, around 170K or more before it needed a rear brake job. Heard it was a pain, and I’ve never messed with drum brakes, so I farmed that one out.

 

Well it sounds like you’re not going to want to do it again then. I know it’s tough but your vehicle is something you don’t want to knowling run to fail. With the miles you’ve got I’d say you got 99% of the value it of those seals and if you factor in ruining your brake shoes it’s beyond 100%. Time to reinvest, buckle down and just do it. It’s quite a cheap fix if you can do the labor.

 

Make sure the diff vent is not plugged up causing oil to be pushed out, pretty easy to remove and clean.

 

Yeah, definitely check and you can always do the two way extended breather mod

 

Would that be something that would be likely to be clogged, with this truck not going off-road? The worst it’s seen is a gravel road or a muddy field, and it’s been years since it saw even that.

 

The breather is the easiest job your facing,I would do it first.

 

Not likely but it does happen, so easy that it's worth looking at. Especially with the mileage you have.
I had an old chevy with a blocked vent tube that pushed oil passed the seals. It happens.

 

Update:

Well, a day or so after I replaced the driver’s side rear wheel speed sensor, the ABS/Brake Warning lamps illuminated again while I was driving on the freeway to work.

So, today, I decided to pull the diff breather and check it. It appeared to be clear, but I went ahead and cleaned it out with brake cleaner spray and compressed air. Just for the heck of it, I decided to pull that left rear wheel speed sensor again, to wipe it off, just in case my issue WAS the breather, and I was lucky enough for the axle seal to quit puking oil.

On pulling the sensor, I noticed that it was very visibly damaged. It had a groove chafed into it, where something in the wheel hub had been continuously or intermittently making contact with it.

In the attached photo, upper left is the original left rear wheel speed sensor that I originally pulled out. Upper right is the new eBay wheel speed sensor I had installed last week. Bottom is a new (right rear) wheel speed sensor, for comparison. So, you can see the damage there.

So, my guess is that I have a failing left rear wheel bearing, and that is allowing some movement in the hub, letting something (possibly the bearing itself?) contact the sensor. The failing bearing also probably allowed enough play in the hub/axle to cause the axle seal to begin to leak, hence the oil that was on the sensor.

Just for comparison, I pulled the right rear sensor to look at it. It is undamaged, but, as I said before, it did have some oil or an oil/water emulsion on it as well.

So, it looks like you guys were right, originally. I’m probably looking at replacing my rear wheel bearings, as well as the seals.

I did some checking, and went by Nashville Toyota and got a quote on the parts. I attached a photo of the invoice sheet. As you can see, the counter man quoted me full retail price originally. The hand-written prices out to the side are what he came down to after I asked if he could do any better. So, he came down some, but not a whole lot. I found the wheel hub/bearing assemblies (same part numbers) on Amazon for $109. The prices on the rest of the stuff were comparable.

So, $879.54 with tax, from the dealer, or, $337.42 with tax, before shipping, from Amazon.

Couple of questions:

1. I was not able to find just the wheel bearing. All I saw online, and, all the dealer sells, is the wheel/hub assembly. If I could find just the bearing and have a shop press the old ones out and install new ones, I could possibly save some money. Anyone have a lead on those bearings by themselves?

2. If I go with the wheel/hub assemblies, can I just remove and replace them, or are they attached to the axle shaft, needing to be removed with a press or BFH?

3. Do those retainers actually need replaced, or can they be reused? The FSM says they get replaced.

 

I have the same issue going on. Replaced my wheel sensors. And there is grease on the new ones and they have the rub marks in at least one as well. I’ll check my breather. Since the replacement of my rear sensors. My Speedo no longer works. Sucks when I try to fix something. Not more is broken. I hope I don’t have to replace my axel seals.