I own a 05 SR D4D xtra cab and have recently brought a transfer case full of mud home from a trip, so breathers have been on the agenda. I made and mounted a breather manifold to inside of RH front guard, used 6mm OD pneumatic tube to connect everything and used sintered bronze breathers. These will still breathe when they are wet, unlike some that have been used on this site.
The front and back diffs are pretty well covered but there is a lot of incorrect information regarding the gearbox and transfer case breathers.
Just a general note on remote breathers - the hose that is attached to the diffs, gearbox etc, will be carrying a small amount of oil vapour and over time this oil vapour will condense into oil, and run to the lowest point. The hose MUST NOT have any low points, it must travel up at all times or oil will settle in the low points and block the hose = breather wont work.
Transfer Case.
The transfer case has 3 breathers, 2 on the RHS that are connected together and the hose goes to a breather somewhere on the bell housing, mine was loose so dont know where exactly. This hose is 4mm ID and can be connected to pneumatic tube using standard fittings. The 3rd breather is on LH side and vents the front / selector compartment of the transfer case and has a rubber cap sealing it from factory. This needs to be connected to the breathers as the compartment on my transfer was 1/2 full of mud and water.
The hose tail is 5mm so I used 5mm fuel hose to connect to this and forced 6mm pneumatic tube into other end and off to the manifold. Transfer case is now fully vented, just have to put rubber boots and console back. Hope this helps someone.
Geoff
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