Adding Diff and Transmission Breathers

The Defender already had a snorkel installed - of course! That's the bit you add on to instantly get more 4WD credibility! But - long before my air filter was going to be submerged, there were a few other things I needed to sort out as well.

Actually, on a Defender TD5 110, most of these things are actually already taken care of – with the gearbox and differentials already being ‘vented’ out to around the top of the engine height. The rear differential has a pipe that runs up to just under the bodywork – realistically, about as high as I plan on getting water around this for a little while.

But, to go back a step, what are breathers? And why do we need them?

Diff and Transmissions, and breathing

As is my nature, when I get into something new (and I am new to 4WDing) I tend to dive in deep and read and watch as much as I can in order to get familiar, and least to a basic level, with the new project.

A subject (or more correctly, upgrade) that kept coming up, again and again, was a wading kit, essentially, lifting up the breathing pipes to a higher level on the vehicle.

Your gearbox(s) and differentials all have liquid in them. As well all know, liquid expands and contracts depending on it’s temperature. This in turn can compress air, or, the reverse, create a vacuum. Now, imagine taking something that has gotten hot during driving, then quench it in cold water – a sudden drop in temperature will result in the fluids compressing, pulling in air, and, if under water at the time, likely water past the seals, and into your oil in the system. Not ideal.

So, to reduce this, the systems are normally open vented – with a pipe running up and out of the way. A wading kit essentially lifts these pipes even higher – up to the same point as (in the case of many 4x4s) the snorkel.


Keep it simple.

There are a pile of kits out there, from basically a pile of pipe sections, through to filtered multi-lined systems with a bracket. In the end, I picked up a simple and cheap kit from Terrafirma via Stag 4×4.

While the kit comes with a pile of pipe – it occurred to me, instead of re-running everything over to a new area – I already had three of the four pipes in one place – so I simply ran the rear diff to the same area, then joined the four and ran the thicker pipe our and up the snorkel.

I didn’t need to use most the supplied pipe, nor a couple of the joiners – simple – quick, which is not how most jobs end up being on my trucks!

If I end up any higher than this in my travels, I will also need a scuba system for myself.

So, simple, quick change – and a great reason to crawl around under the truck and see what else needs doing…

Popular articles

Kerry Adams
Kerry Adams
A constant learner with an inquisitive mind, Kerry created The Bloke as a way to share what he was learning from the community of experts he found himself surrounded by. Precision Shooter and GunSafe soon followed. Somewhere along the line, he picked up one or two things himself. But don't call him an expert.