rear differential pinion seal leak and breather plug

[cb97alltrac]

Have a small rear differential leak and now its throwing gear oil up under the van. Level was ok so must be new. Checked the breather plug on top the differential and of course it was totally plugged and rusted shut, which I assume is the cause of my leak. No oil at the rear wheels or axle. I replaced the breather plug but still leaking so am doing the rear pinion seal.

Checked my other van and the breather plug was clogged as well, but no leak yet. Wise to check differential for any leaks and check level and make sure breather plug is open and not frozen before any leaks develop. I used a 6 point 24mm socket after spraying rust penetrant to get fill plug off cause its easy to round it off.

[cb97alltrac]

I'm not a great shadetree mechanic but this was harder than the youtube videos suggest. Needed a 4 ft cheater bar to break the pinion nut loose, even after I unstaked it.. Needed a 3 prong seal puller to get the companion flange off
Old pinion seal would not come out with vice grips, seal puller tool, or screw driver or hammer and chisel, seemed like it was rusted in place. Finally rented a slider hammer with a hook attachment and it popped right out first try.
New seal was difficult to put in, very tight, even with hammering a 2 inch pvc endcap contacting the metal periphery. Hard to get started equally, finally did after slight sanding of the outside rim.
reinstalled the flange as premarked, and tightened the pinion nut to exactly where it was before per the marks I made., used red threadlocker and then restaked the pinion nut. Took me all day. Doubt I will ever do this again, even considering the $410 I saved. I would recommend a professional do this.

[zak99b5]

Good news is, you should never have to do this again

[Jonny]

First time doing the pinion seal replacement for me so I thought I'd add to this thread with some pics. There is a pretty good thread on the Vans forum - https://www.toyotavantech.com/forum/...t=differential - and a blog here for the Previa - https://www.toyotavantech.com/forum/...Rear-diff-seal. The Van process seems very similar to the Previa, and both these links should be read. I only found the Van one after the fact so didn't check the bearing for play.

Here is the breather the OP talked about...

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Under all that crud is a hexagon for a wrench. It is not screwed in with much force and mine came out very easily. The cap is staked on.

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You should be able to blow through it easily from the threaded side, and suck through it with difficulty. If all's well just put it back in.
If not:
Prying up the staked part, this is what's underneath... (restaking is slightly annoying so don't disassemble unless you have to).

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OK, on to the main business - the pinion seal
If it's leaking you'll see oil here, and if it's bad, it will be sprayed all over the undercarriage. (photo is upside down)

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I took the whole drive shaft off so it was out of the way, and I could more easily regrease the forward U-joints which have a replaced joint, and spread grease all over the shaft to discourage rust. Mark flanges of shaft and front and rear companion flanges before removing. Tap shaft flanges with plastic mallet if stuck.

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This is the rear differential companion flange, held on with a 24mm nut and big fat washer.

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I ground a punch to the shape of a small chisel tip to unstake the nut. If the nut is totally unstaked it likely will not require excessive force to remove. I'd guess mine came off with about 100 foot pounds. When you start turning this nut, the van will want to move. Make sure you have the hand brake on tight, the vehicle in 1st or park, and the wheels chocked. As soon as the nut has broken loose, unscrew it with your fingers, counting the turns until it comes off. This number, plus the stake mark, will let you know the original position of the nut when you reinstall it.

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The flange came off by gently tapping around the edge from behind with a plastic mallet. The flange and dust cover come off together. I marked the flange adjacent to the groove in the shaft so that I could position it in the same place.

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Look at the flange collar - it has a distinct groove. Just a guess, but I suspect this was not there when the part was new, and has worn in there after 290,000 miles of spinning with dust and dirt ingress acting as abrasives on the seal lip.

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Here's the seal. It is set about 1/16" below the edge of the diff housing...

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Here's the new part I got from the dealer...

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Hmmm. They don't look the same at all. But I checked the part number from the parts diagram and it seems to be the one Toyota wants you to use. Maybe it's new and improved?

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I have no seal puller and didn't like the idea of prying with a screwdriver because of potentially damaging the shaft splines or the machined seal seating surface, so I drilled a hole in the middle of the sidewall, broke it apart with a screwdriver then mini vice grips, then got a small cat's paw into the opening and it came out nicely.

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Yes, different parts. My theory is that the added rubber flange in the front is to make a better seal into the dust shield to make it less likely that the flange collar gets grooved as shown in a previous pic

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The glue flange part of a 2" PVC pipe is a perfect size to use for hammering in the new seal. Cut a piece about 2-1/2" long and buy a cap for it so you can hit it in the center with a mallet. It's hard to get the seal started straight. A good forceful tap taking care to have everything perfectly square, including the mallet, seems to work.

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In order to try to have the seal lip riding on the part of the collar which wasn't grooved I pressed it in so that it was only dead flush with the diff case, not all the way seated to the little machined step inside the diff.

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Since I had the theory about the rubber flange sealing against the dust shield I put a bunch of grease in there prior to reassembly.

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I had every expectation that the flange lock nut would go back to its original position without any problem. This was not the case. By the time I was 1/4 of a turn shy of the original spot it was taking a lot more force to tighten it than it did to break it free. Since the gent who provided the information contained in the blog linked above said don't overtighten, and he is a lot more experienced than me, I staked it in the new position. Anyway, so far no leaks or bad noises. Hopefully this helps someone, or at least entertains them for 10 minutes.

FWIW - when I got the part from the dealer the guy said they probably wouldn't be getting these in any more since the part looked like it was being discontinued. It's one of those which is very reasonably priced - $12.

[cb97alltrac]

Nice. Thanks for the writeup. Slidehammer was the key when I did mine.