Differential breather relocation?

[BigJ]

Anyone know anything about this? The Raptor's wade line is at 30", but the manual clearly states that if the differential submerges, replacing the fluid is required. All I can figure is that's because there's a breather under there somewhere below the wade line.

If that's so, any reason we can't relocate it higher up? Above the wade line?

 

[MagicMtnDan]

Good idea Jason.

So far I found this (older model F150 but it's worth checking out for sure): http://www.ford-trucks.com/forums/884308-rear-differential-breather-mod.html

Another (older model info): http://www.fordforums.com/f107/rear-diff-breather-52378/

 

[bstoner59]

I believe our breather tube goes up and connects to a rail on the underside of the bed??? look behind the driver rear tire and see if that is the right one

 

[Falcon]

I PM'd FMS06 on this one... nothing like having access to a Ford Senior Master Mechanic <G>. Now that I have sent him the right link (oops) I am sure he will weigh in.

Falcon

 

[BigJ]

Good thinking Falcon. I haven't crawled around under there enough to see if B's right. Good to have FS's thoughts on this.

The FJ guys have what they call a "scuba mod". Junior, our resident and most beloved FJ troll just installed one this weekend. Looks like a really clean package that, in theory, we should be able to replicate fairly easily:

Pics borrowed from Junior's photobucket, as posted in his thread here: http://www.fjcruiserforums.com/foru...111-gonna-start-modding-old-girl-weekend.html








(the two lines are from both the front and rear breathers)

 

[MagicMtnDan]

I've seen that "Scuba Mod" before over on the FJC forum. Cool to see it in detail. Where are they getting what looks like a machined block (is that anodized aluminum) for the manifold?

Hey Junior, does your FJ have the dreaded "fender bulge" - you know, that feature that Toyota designed into their purpose-built offroad vehicle? (Sorry but it's what kept me from ever getting serious about the FJ). Oh, and how many windshields have you replaced? (Man I spent too much time over there).

I hope to see you on the trails Junior. I know FJ's are very capable offroaders and they're fun to modify.

 

[FSM06]

Hey fellas, I would have chimed in sooner, but wanted to look at mine for the exact location of the breather. bstoner is correct, the vent line extends from the differential housing up to one of the cross supports of the truck bed. If you plan on doing alot of water crossings or "wading", extending the breather(s) is a good idea. I am VERY impressed with the pics above of the "scuba mod". It is extremely clean, the air line fittings are an excellent way to "seal" the fitting , and it is compact making it easy to route to a suitable location.

Most water crossings such as creeks, washes, etc. are fairly short and do not facilitate the differential housing being under water for long. In these instances, along as the breather is above the waterline, then changing the fluid is likely not necessary. If the differentials are under water for extended periods of time (like a truck that backs a boat trailer into the water regularly) then my concern would be the water ingressing from the three sealing points. (2) axle seals (1) pinion seal. Lip seals are designed to keep fluid from exiting the the axle housing while keeping dust/dirt out. They aren't necessarily designed to keep fluid out. During extended use under water, they could actually "draw" water in.

Personally, I don't believe that under normal 4x4 operation and occasional water crossings that this is too much of a concern. JMHO

 

[MarkT]

Lip seals are designed to keep fluid from exiting the the axle housing while keeping dust/dirt out. They aren't necessarily designed to keep fluid out. During extended use under water, they could actually "draw" water in.

I agree... just want to add one point. Heat. Especially when towing a heavy load on a hot summer day the rear axle can get very hot. The sudden cooling that occurs when the axle housing is submerged in cold water can reportedly create a vacuum strong enough to pull water in past the seals.

At first, this might not sound possible if the vent is above water and not blocked, but most vents are fairly restrictive and cannot equalize a sudden pressure change instantly...

 

[Junior]

Ahoy! Let me give this the time it deserves, and take some pics of the rest of the setup - the pics above were taken for an audience that was familiar with that particular kit. I can do it better than that fer ya.

It's a pretty slick setup though - that blue ****** you see up there is a polyethylene breather which is kinda like Gore-Tex: water molecules can't penetrate it, but water vapor molecules can... and yeah, billet aluminum for the manifold. Total cost with shipping $70.

There are actually five different things that get vented higher: rear diff, electronic locker, front diff, transfer case, and transmission. Each has a breather already, and the front three are mounted fairly high in the engine compartment, but if you're in there doing it, you may as well do them all.

It's about the change in pressure that happens from a combination of two events: the units cooling down too quickly (from being hot and then being submerged), and then the breathers being underwater when they equalize pressure (thus sucking water in). You can sink the diffs if they're cold without worries - it's just that when they're hot, and they cool down quickly, air must get drawn in - the breathers are there to let that air in there instead of past the seals - but if they're underwater... [EDIT: Mark, above, has it right]

More later.

 

[MagicMtnDan]

Thanks Junior! Glad to have you helping us Raptor owners.

Hope to meet you on the trail soon.