Thread: Diff Breathers, DIY how?

I made up a set for my Rangie using 6mm or 8mm control tube, Tefen fittings and Finger Filters. ( check out your local irrigation supplies store )

The front diff, I ran up behind the brake booster servo, and the rear diff led up into the fuel filler cavity. Had no issues yet.


Then again...... I haven't crossed any water yet!

A pneumatic 1/8 BSP swivel elbow to 6 or 8mm tube (nickel plated brass) should cost about $3.50 (PM me if you need them, I'm in the trade). Pneumatic tubing tends to be expensive because it is rated to quite a high pressure, which is not needed for a breather, irrigation tube should be OK. 6mm OD Nylon 11 is about 90c/metre, polyurethane (much more flexible) about $1.30/metre
A lot of people fit a pneumatic silencer to the end of the breather but I don't think this is needed. The axle doesn't 'breathe' as such, it's just to allow the pressure to equalise if the axle is hot and then suddenly cooled during a water crossing for example.
On the Defender the end of the tube has a U-bend so it ends up pointing down. Less chance of dirt getting in and if you did submerge the car there is less chance of water getting in (as the water rises it raises the pressure in the tube/axle slightly which may then resist further water entry).

BSP thread sizes date back to the days of cast iron pipes. The size relates to the bore of the cast iron pipe so 1/8" BSP was the thread on a 1/8" bore pipe which needed a heavy wall thickness to give any sort of pressure rating. With material advances tube wall thickness has decreased but the thread size has stayed with us. The smallest BSP size is 1/8" (not much call for bore sizes below 1/8" back then) in pneumatics smaller sizes are metric eg. M7, M5 & M3.

Colin