I have read hundreds of post out there pertaining to this issue, and have had to experience it first hand. I have even read where folks have had to replace their seal/bearing several times. Toyota issued a re-designed oil seal, but the seal is only the after fact. Yes the seal is leaking, but why. The root cause to why the seal failed should be found! Oil seals have been used for many years. The oil seal in the rear axle is no different than that of a front and rear main crankshaft seal. I have a 93 Toyota 4x4 with 250,000 miles on it, and I've never replaced my crank seals, so why am I and others replacing axle seals so frequently?
First…If your seals have failed, check your differential vent before proceeding. If the vent is clogged, the pressure will find the easiest escape, which is the oil seals.
The rear bearing (SBB) sealed single ball bearing for the Tundra is manufactured with about .5mm (500µm) of axial clearance to compensate for axial run out (horizontal fluctuation). Toyota obviously had axial run out in mind when designing the rear axle. So knowing there is some axial run out, why is the retainer that the oil seal rides on so narrow (6mm). The OEM retainer that the oil seal rides on is approx. 6mm wide with a large chamfer on the end facing the differential and a small chamfer on the hub side. This retainer has to be installed in the precise location or you stand the chance of seal failure. Due to axial run out, heat expansion, etc., the seal will ride on the chamfer at times. Hence, why I’m complaining of it being to narrow!
I designed a new retainer for the seal to ride on. I do not and will not sell them however, I will share my design (free) for those of you that have the capability of having them machined & tempered through a heat treat process. The new retainer is approx. 15mm in width vs. the original at 6mm. If installed where the retainer bottoms out on top of the ABS sensor, the oil seal will ride on the center of the new retainer. Before installing the new oil seal, you must use a die grinder to open the bore of the axle housing behind the oil seal to accommodate for the extra length of the retainer. When opening the bore of the axle housing, be sure to port at the 12, 3, 6, & 9 o’clock quadrants of your bore to allow oil flow to the oil seal. This is very critical in the life of the oil seal. The oil seal must have sufficient oil flow or it will harden and become brittle.
I am in the bearing business, and specialize in differentials and rear axles. I'm not trying to sound like a know it all (KIA), I'm just expressing my experience in this business. I have seen many designs in & out that are out there, and this is not one that is bullet proof by any means. I hate to say that because I would not & do not own anything other than Toyota products. I would be a free spokesperson for them if they wanted! We all have brain farts some days, and the design engineers on this particular rear axle did that day. Through my contacts, I have been in discussion with domestic engineers (not customer service) at Toyota, and the fortunate but yet unfortunate side of things is that there is no safety issue, therefore no recall. The 07’s and up Tundras have had a similar issue, but they are from a completely different supplier than those of the Gen. 1 Tundras. I hope this information can help some of you out there that has had to do this multiple times. If you have any questions, please feel free to email me at [email protected].