Did rear axle breather mod...axle under pressure.

For what it’s worth, I did the rear axle breather mod today on my new Pro. When I unscrewed the factory “vent” it released a fair amount of air pressure. The axle was cold and the truck had been parked all night. My guess is the stock vent wasn’t venting. Might want to do the mod so your sure it’s venting. Pressure buildup can cause leaks past the axle and pinion seals. FYI only. YRMV.

 

Are you sure it wasn’t drawing air in? That would make more sense for a cold axle. The OEM valve is supposed to prevent a cold axle sucking water in.

 

Nope...I’m not sure. Either way, the stock vent wasn’t venting. It was 80 degrees today so no huge temp fluctuations.

 

My understanding is the stock breather is a one-way unit. It will allow expansion of the air in the diff to be vented, as it warms up, but will only allow air back in very very slowly to avoid sucking water in a river crossing etc., when the diff cools down.

I’ve not proven this, just what I read about it someplace.

 

I just did this mod. after 2 days, the axle was still under "vacuum" when i removed the stock breather. wonder if thats how they keep it from leaking! LOL.

 

That's correct.

 

That’s actually a positive observation. Clearly Toyota has put some engineering into that OEM breather if it will hold vacuum that long. I believe that is the intention, not to allow suction. When I did my diff oil change the rear diff was under vacuum as well, so the OEM breather was not letting the outer atmosphere into the diff as it cooled down.

 

same here. also makes sense as to why would they relocate the trans and front diff breathers and leave the rear on the axle. It's not an oversight.

 

I’m confused. I’m right about to do this mod, came here to check for ideas on where to route and place the breather valve. So is this mod not a good idea??

 

I'm not saying its not a good idea if you definitely going to be in deep water a lot. But I think it's not needed for 99.8% of owners including those that go off road. If it was a concern, they would have relocated it higher like the other two in the front is my thoughts.