Diff breather - pressure in diff?

just finished the breather mod and when I was taking the old valve off the diff there was quite a bit of air behind it. I feel like there shouldn’t have been. Was the old valve plugged? I’ve got to re use it until I can get to the auto parts store (an hour away) and get a fuel filter for it. Any suggestions? Is something not right?

 

Pretty common. Get it replaced. Many run a hose making the breather higher up. Some run it to the gas filler area.

 

Yeah it’s up in the taillight now. I’m going to get a new valve for the end in the tail light but for now I’ve got to re use the old one which I’m assuming is clogged.

 

Simply twisting the cap until it's loose usually is all that's needed. It's easy to do when it's still on the rear axle. You might need to put it in a vise. When loose the cap will feel very loose.

 

To unclog it?

 

Yes. the stock breather has a spring and a rubber disc in it. As the third member breaths a slight amount of oil comes out. As it meets with dirt in the air it creates a sludge that dies and plugs the breather. By twisting it you are breaking up that sludge. The cap fits very loose. It's possible that the rubber disc is stuck but over 36 years of having Toyota pickups I've only had dirt getting into the cap. You can easily tell. Hold the breather by the hex/ threaded part and try to twist the cap. If it doesn't feel loose then there's a real good chance that it's just dirt.

 

It’s a one-way valve. It lets air out but doesn’t really let air in. Are you sure it was pressure and not negative pressure?

 

Back when I was into playing in the mud I would just pull the cap off. It's just held on with 4 crimps at the base. I would then just slide a rubber hose over the base and use a hose clamp to hold it on. I would just put a loop in the hose and then run it up by the taillight or side of the bed. I never bothered putting anything to keep dirt out. When you think about how much (or I should say little) air actually goes through it I'm not sure that it could suck anything in. The only time it's actually pulling air into the axle is when it's slowly cooling down. It's not like a breather for an engine.

 

I’m not really sure now that you mention it.

 

Most likely some negative pressure. Makes sense as I drove to my garage to do it (away from home). That Hanks @15whtrd

Also. Cap was stuck. Already had it on the hose and zip tied in the tail light but took a 14mm wrench the base and some pliers to the cap and loosened it. Thanks @Dr_Al

And air in the diff now should be able to escape.