I hope that by opening this discussion we can have more people contribute to this analysis with a critical eye the next time they have to dig into the rear axle. I believe I have found why Tacoma and 4runner axle seals continually leak. Some would say I am overthinking this. I look at this as a common and incredibly expensive repair for most owners of these trucks. So let me start by saying this. The seal does not properly sit on the retainer. There is no way to get the seal to correctly sit on the retainer in ts original configuration. I say this because I have physically pushed the un-installed retainer into the installed seal and the retainer will grind on the axle housing before the seal could be centered on the retainer shoulder. A basic design flaw when Toyota switched from a flat seal to a angled seal in 2003. They redesigned the seal but not the retainer. My last observation is this, if the vent is clear and the bearings in good condtion, you may still be leaking and the oil is pooling in between the inner and outer seals. Its not until the vent gets blocked that the oil is forced out of the axle housing and onto the brakes. Again this is my theory and I'm looking for productive input from members here. No cheap shots or personal attacks please. So lets begn.


Theory: the retainer is not making contact with the seal correctly and allows oil to leak past.

Observation: my seal when seated in the housing all the way in,would ride right on the bevel edge of the shoulder of the retainer. Any wobble would let oil get by the seal. The retainer had a polished ring near the edge. You can see the ring next to the bevel in the top photo

Solution: I just re-did the seals for the forth time in 3 months. I found that no matter how I installed the seal it didn't sit on the retainer far enough. I even tried the Timken seal 1960 but the rubber was too stiff and it failed in two days. Its a crappy seal, stick with oem. My solution was to install new retainers backwards so there is more of the shoulder for the seal to ride on. I also moved it inboard by 1mm plus the 3mm i gained from not having the bevel there anymore equals an extra 4mm of shift in placement. If you go more than about 3mm inboard with the retainer, it will rub the housing. So 1mm is all i wanted to move it. By doing this, it will allow you to seat the seal all the way into the housing squarely. Here's a couple of pics.

Old config
[img]http://im1.shutterfly.com/media/47a2db24b3127ccef05e04e944e000000040O08AZM2zNo3cNQe3nws/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/[/img]

New config
[img]http://im1.shutterfly.com/media/47a2db24b3127ccef05f120fe57100000040O08AZM2zNo3cNQe3nws/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/[/img]

Status:
5/04/2012 installed
5/27/2012 and still dry

When you install the axle, use MP grease on the seal and put gear oil on the retainer and be careful inserting it into the seal. Dont force it. Once it lines up it will slip into the seal nicely. The edge does have a mild bevel to it so it won't damage the seal if you don't force it. You will know that you are in the sweet spot if you feel the resistance of the rubber seal 3/16" before the bearing carrier plate mates up to the axle housing. That will put you dead center on the retainer.

* don't assume the original inner retainer is in the correct position. If your axle vent is clear, it probably wouldn't have leaked if it was positioned correctly. I would suggest before disassembling the axle, install a new seal in the housing and test the position on the retainer with grease to make sure it will be correct. I used the new retainer to check how deeply it could be set into the seal. It turns out that the retainer bottoms out on the housing before it will flush up with outside of the seal.

I have read discussions of only partially seating the seal so it sits on the retainer better. I tried it and I personally couldn't get the seal to square up properly.

I think this may well be the solution to this problem.

Feel free to share your thoughts.

This is an image taken from the TSB regarding the seal redesigned in 2003. If you notice the old seal had a long flat contact patch which would sit upon the shoulder of the retainer extending all the way to the outer edge of the seal. In the newly redesigned seal, they changed it to an angled contact point, but that contact point is too far inboard (now near the inside edge of the retainer) and rests not upon the shoulder but on the retainer's bevel.

This could explain why even new seals are failing simply because they aren't seating on the retainer at all. The TSB link is below the picture.

[img]http://im1.shutterfly.com/media/47a2db29b3127ccef0452bd2db4300000030O08AZM2zNo3cNQe3nws/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/[/img]

"http://toyota.justanswer.com/uploads/skyvisions/2008-05-30_135400_02_seq1.pdf"

The new OEM seal design allows for a lot of flex. Even with the retainer big side in, it goes in easily. This wouldn't work as well with any other seal like Timken or National brands.

[color:"DarkRed"]Video discussion:[/color]
http://www.youtube.com/watch?v=9tdGpmpNRFU

:2cents:

Compare the non-ABS axle to the ABS axle and you will quickly notice that the seal of the non ABS is pressed right up against the bearing. That means that if your seal is not pressed right up against the ABS exciter ring, the seal is not sitting on the retainer. But you cannot just push the retainer deeper into the axle housing because it will rub the housing.


[img]http://im1.shutterfly.com/media/47a2db03b3127ccef0795614fef300000030O08AZM2zNo3cNQe3nws/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/[/img][img]http://im1.shutterfly.com/media/47a2db03b3127ccef078b3191f6800000030O08AZM2zNo3cNQe3nws/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/[/img]



Clearly you can see when you view through the ABS sensor hole, the seal is nowhere near the ABS ring.

[img]http://im1.shutterfly.com/media/47a2dd23b3127cceffd0dc2c97e100000060O08AZM2zNo3cNQe3nws/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/[/img]
This picture was taken after the bearings were changed and the the first seal failed. the retainers were setup using messurements from the FSM 122.2mm +-1mm. I found it needs to be 124mm with the retainer flipped.

For the people who may want to tackle this DIY and are not sure what the grease test is, here is a picture another forum member provided to me (since I forgot to take this picture when doing mine). Mark tells me he left 3mm of the polished ring inboard of the retainer and once installed, using grease on the retainer and spinning it a few times, it will leave a foot print of where the seal lip is positioned. Note, the bevel is outboard and the retainer shows the seal riding in the center of the retainer.

[img]http://im1.shutterfly.com/media/47a2d831b3127ccef0015382026200000030O08AZM2zNo3cNQe3nws/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/[/img]

*When you take your parts to a machine shop, consider printing this picture and bring it with you.