Greetings. Bottom line is my recently replaced inner rear axle seals are both (left and right side) leaking. Here's the story.

On my '97 4Runner the rear axle housing was rusting out badly at the differential. I read this is common in the eastern states with road salt. So, this summer I found a used axle housing out of OR, had it shipped in and did the full swap. This included:
- new differential breather
- new inner seals (National #1960 from Advance Auto as opposed to Toyota #310-5006).
- new Toyota parts for both sides: bearing, outer dust seal, big O-ring, snap ring (I was able to re-use the retainers)
- for the removal and installation I did not use a press but rather was able to perform the overhead slam on concrete approach (Replace rear wheel bearing...) to separate the two retainers, speed cnt. rotor, and snap ring.

Everything went back into place fine. The new inner seals were no problem to install and seemed to be in correctly. The truck probaby only has 600 miles on since rebuild. Now I find leaks on both sides (soaked the new shoes too.) So I removed the axles and have both on the bench. Inner seals look fine. The outer retainers have polished rings suggesting the inner seals are riding properly. I do note there is play in the bearings but don't know if is normal or not.

Could it be:
- Should have used Toyota inner seals vs. Nationals?
- I saw a post by someone who replaced seals 6 times to no avail and finally deduced the whole axle housing was bent. Seems like a long shot?
- Maybe the new bearings are bad having play that in turn leads to leaks at the inner seals? With the axles now on the bench I find there is play in the bearings when holding the backing plate and moving the axle up and down. I don't know if play is normal.

Thanks for insights you might offer.

One long shot question... but have you driven thru water since your seals were done?

2. do you have your diff breather extended??

not sure if thats your issue or not, but just thought I would start there considering the low mileage since your seals were done

Why would you ask that? Do you think a breather extension can cause a leak?

The reason I'm asking is that I have a leaky left seal on the rear end and I have the breather extended.

Sorry for my confusion, but if it's leakin diff fluid to the shoes then u have an outer seal problem. I have advance auto seals and ive been fine for a few months with heavy wheeling and full submersion to salt water for several hrs and I've been fine. First instal I did have a leak since I didn't have a socket big enough to nock it in. Get a bigger socket!/ flat piece of stock.

no, Im asking because if he got his seals changed and then went thru a couple feet of water without an extended diff breather, he could have gotten water in his diff which would cause his seals to leak so soon after replacing them.

of course, it could be cuz he got crap ones installed last time, but Im giving the seals the benefit of the doubt right now. LOL

Why would a couple feet of water, even for a few hours cause the seals to leak? Wouldn't the factory breather let the ingested water out, or not? Sure there would be added pressure from the extra volume of internal space but isn't that what the breather is for, at least as vapor goes? I never sank my rear end without the thankful breather extension so I wouldn't know. I can see a breather mod backfiring if it was too short and kinked in a "long left" flex, as the rear was already very hot and then someone left it in a distorted position where the breather was kinked and could not do it's job for I don't know how long but maybe blew out a seal.

If you've had these installed and not done it yourself then I don't mean to be the A-hole that says "that's why I do it myself" but you need to bring it back to the installer and have them do it again and again until it's right. If they dont do it right then take ur $ back and go to someone that knows what they're doin! Good luck man, hope all goes well. I used to work in a small Corvette shop and we did a lot of other vehicles that we weren't "certified" on but still knew our way around the grease and wrenches. That being said, if we "mechanics" F'd sumthin up on a non-Vette vehicle it was on the boss and we'd take it back and fix it, if not then $ was delt with and the customer was sent to the nearest expert.

its all about temp with the diff breather, with cold water and a hot diff a quick temperature change would cause a diff to cool quickly and suck in air, if the diff tube is under water, it would suck water into the diff...

thats why you do a diff breather, theres no point otherwise.

again, I only asked the OP if he went thru water due to the quick nature of his seals failing. Giving the axle seals the benefit of the doubt til we know if the OP was galavanting thru streams shortly after without an extended diff breather...

Thanks for the ideas. I did install the breather extended up to the gas cap area.

I replaced my drivers side due to leaking, for preventive maintenance I replace the passenger side. Now the pass. side leaded within a few hundred miles. I replace the wheel bearing since it had some play in it upon closer examination. It still leaked. Found that I put the seal in backward, replaced it again and it's been fine. I've also read about not hammering it in too far, but it's been awhile since I was reading about this.

Cool, that rules that out, I think we are looking at faulty seals then most likely...

or bad install?

First: When the axle seals go bad on these gens it is almost always the inner seal, not the outer seal. It seems counterintuitive that an inner seal would be easier to replace than an outer, but that's the way it is on these runners. Replacing the outer seals requires destroying some otherwise good parts and using a press. Inner seals can be replaced in your driveway with ordinary hand tools.

Second: If you keep going through axle seals as described then you have a bad axle housing. The entire housing will need to be swapped. I'm on my 3rd now. 1st went with an accident. 2nd was a bad salvage. 3rd is a good salvage. No e-locker housings should be easier to come by and relatively cheaper.

Thanks. I am indeed focused on the inner seals. A Toyota rep today validates that Toyota had trouble with the original seals and has since changed the specs and offers an updated seal #301-5006. Speculation is that aftermarket seals #1960 may be based on the old specs and thus be prone to fail.

As to your bad experience with a replacement axel housing, that has me concerned as noted, I replaced my housing with a used one. It sure appeared fine. Any way to further determine if this is a factor? At this point I am inclined to replace my bearings (despite being practically new they seem to have play - Toyota rep will likely warranty them) and put in new seals (OEM this time) then see how it all holds up.

You could have a machine shop test axle runout just to be certain that the axles are fine. I had an axle replaced believing that was the problem, but leaks just kept happening. I don't know of a way to test the actual housing though. Even the FSM states that if seals keep leaking, replace the housing.

My story closely matches that of practical.
I dismantled my rear axle because of an axle leak. I found my wheel bearing was toast on the driver side. I had Toyota press on a new outter seal, bearing, both retainers and ABS rotor onto the shaft. After installing a new Toyota inner seal and putting it all back together again it was only a few days before I noticed the smell and drips on the driveway from gear oil.....again!
I found, after much head scratching and digging, that on an ABS rear axle the ABS rotor and the bearing retainer #2 that the inner seal rides on should be pressed a certain distance onto the axle shaft. You (or Toyota service technicians) can press the ABS ring and bearing retainer #2 too far. The dimension given in the Toyota service manual is 122.2mm +/-1mm or 4.811" +/-0.039" from the face of the flange where the brake drum seats (rear axle hub with wheel studs protruding) to the inside (opposite side) of the #2 bearing retainer. To clarify further, the order of parts on the axle shaft starting from the outside working in is the outter seal, wheel bearing, bearing retainer #1, C-clip (or snap ring?), ABS rotor, bearing retainer #2.

I found there should be a space between the C-clip and the ABS rotor (about 3/16" on my axle). Toyota pressed the retainer #2 and ABS rotor all the way down to the C-clip. The inner seal had nothing to ride on to seal the axle.

I took the axle back to Toyota and the "head" mechanic looked at it and instantly said "hmm those parts are pressed onto the axle too far". they reworked the axle for free and provided me with a new inner seal. (I should have gotten half off on brake shoes too!)

I have the axle back together and no more leaks.

Agreed. I did the same thing. Now I have Toyota seals and they seem to be holding up. Good luck.