[jman1200]

My rear differential started leaking, occasionally I would find one or two drops of oil on the garage floor.
I looked under and noticed that it was leaking through one of the oil seals, long story short, it was being caused by the vent being seized, this is one of those parts I thought to be maintenance free... big mistake.
I removed the vent (pic 1) and it looked like a one piece component. I dipped it in a strong solvent and waited a while but still, one solid piece (pic 2). I tried to blow air through it and nothing. I then decide to risk it and took a wrench and pliers and twist it (pic 3), it finally moved and a lot of debris started falling down. I cleaned it pretty well and reinstalled it.
I then changed the oil (pic 4), removed the fill plug (pic 5) and the drain plug (pics 6 & 7), this last one was full of old oil (almost grease) around the magnet. Finally added the new oil (pic 8 ) and torque the plugs.
I strongly recommend all AWD owners to check this vent at least after every winter (maybe its in the manual and I never noticed it), get under and try to turn vent cap with your fingers, if you can't, remove it and clean it.
I hope the pics help.

 

[robo5]

Great tip.

 

[shineysideup]

My rear differential started leaking, occasionally I would find one or two drops of oil on the garage floor.
I looked under and noticed that it was leaking through one of the oil seals, long story short, it was being caused by the vent being seized, this is one of those parts I thought to be maintenance free... big mistake.
I removed the vent (pic 1) and it looked like a one piece component. I dipped it in a strong solvent and waited a while but still, one solid piece (pic 2). I tried to blow air through it and nothing. I then decide to risk it and took a wrench and pliers and twist it (pic 3), it finally moved and a lot of debris started falling down. I cleaned it pretty well and reinstalled it.
I then changed the oil (pic 4), removed the fill plug (pic 5) and the drain plug (pics 6 & 7), this last one was full of old oil (almost grease) around the magnet. Finally added the new oil (pic 8 ) and torque the plugs.
I strongly recommend all AWD owners to check this vent at least after every winter (maybe its in the manual and I never noticed it), get under and try to turn vent cap with your fingers, if you can't, remove it and clean it.
I hope the pics help.

Thanks for the big tip! My van has around 200k on it and the breather was indeed stuck also. I think that anyone with and awd model should be looking at this! I haven't had any leaks and maybe won't thanks to this website!

cheers,

shineysideup

 

[Bchristofferson]

I know what I'll be doing Saturday. How is the '04 holding up? Do you still have it?

 

[jman1200]

Haven't been around for a while, yes, still have it and its now my daily driver. Bought a 2015 Pathfinder that became our travel/towing vehicle which is nice but far off from the comfort and roominess of the Sienna.

 

[FlashJT]

So how did you determine the leak was caused by the vent and not actually a bad seal? I've got a little leakage and was going to replace the seal(s), but will have to check the vent first in case that's my problem.

 

[jman1200]

Simple physics.

The air and the oil inside the differential expand as they heat up, if the vent is clogged/seized the air will build up pressure and the next weakest point are the oils seals. The pressure will push air and some oil through the seals.
I posted that in 2010, seven years later it hasn't leaked back once. Back then the dealer wanted $800 to replace the seals.

This applies to the transmissions as well. I recently bought a used Mazda 6 with a manual transmission which I found to be leaking... guess how I fixed it...

Not saying this will always be the case but definitely the first and cheapest thing to do.

 

[Oldwolf]

Do the Gen3 differentials have the vent too?

 

[K. Carew]

Do the Gen3 differentials have the vent too?

Yes and I can't seem to get mine off. It doesn't screw in. It just sits in there. Kind of weird

 

[ForestRoads]

Anyone know the wrench size for this?

 

[K. Carew]

Anyone know the wrench size for this?

I believe it was 21 mm.

It was pretty large. And a lot of torque to get it off.

 

[AWDSiennaSMH]

If the rear carrier assembly goes bad, can the internal gears be removed so the van can be driven as FWD only?