1078 Pre Fording Plug Locations

[Scott z]

Would anyone have pictures or a better description of what needs to be plugged on a 1078 prior to driving in high water?

Where is the bell housing plug?

Does each axle also have a vent that needs to be plugged?

Last but not least, while having some transmission work done I was offered the option of installing an extension hose which connects to the breather opening on top of the transmission. Strange that this isn't something installed at the factory and seems like a good idea.


Thanks

 

[dronsen]

Scott-

See page from TM attached for location/setup. Axle vents all run to inside of frame rails - location depends on model.

 

[Awesomeness]

If that picture is a little confusing (it was to me originally), don't let it fool you. When you're laying underneath the truck, looking up at the bellhousing between the engine and transmission, there is a rectangular plate (pictured) right on the bottom. The plug stores in the threaded standoff, and you simply move it into the hole.

 

[Scott z]

Anyone know what the purpose of the normally exposed hole is?

What is the downside of plugging it full time or for several hours assuming you are expecting high water?

 

[coachgeo]

Anyone know what the purpose of the normally exposed hole is? .... What is the downside of plugging it full time or for several hours assuming you are expecting high water?

hre is some info from ARB

A differential / axle breather serves the important purpose on a 4WD vehicle of venting the air pressure in drivetrain assemblies such as the differentials, transmission and transfer case. Under normal operations, these assemblies heat up and the air inside expands, increasing the pressure and thus the need to be vented to the atmosphere is created. When the drivetrain assembly cools down the air inside contracts and creates a vacuum.

Many drivetrain assemblies are fitted with a breather from the factory. These factory breathers are usually a one-way valve mounted directly to the housing or remotely on a short tube. The shortfall with the factory breathers is that driving through water crossings creates a vacuum caused by the drivetrain assembly being cooled rapidly by the water. This vacuum will tightly close the valve shut causing air to be instantly drawn into the assembly through the seals. Many times the seals are still submerged below water, leading to the water being drawn into the drivetrain. This will contaminate the oil and possibly damage drivetrain components.....

Now interestingly... ARB produced a product for breathing vs highwater..... the above came from this http://store.arbusa.com/ARB-Differential-Breather-Kit-170112-P22783.aspx

 

[Suprman]

The breather lines are on top of the axles routed up. I believe the bell housing hole is just a drain hole.

 

[Scott z]

Thanks coachgeo and superman. Good info but I'm still unsure about the bel housing plug.

The breather is located on top of the transmission. Mine has the remote breather which is simply a long hose routed to a higher location but either way it's clear these top mounted breathers allow air to expand out of the top of the transmission.

The bell housing plug hole still leaves me scratching my head. It's located on the bottom and clearly there are no fluids inside as they would simply drain out...so what is this hole for?

How long can can it remain plugged without causing any damage?

 

[coachgeo]

So there is not " Pre Fording Plug Locations" but just one location that is a drain. Thanks for the clarity. Could not fathom that the typical breathers in the FMTV line as described above were not plumbed up high enough to need a temporary plug or valve change. Heck even my TJ was plumbed up to hood level. Just the one drain plug makes a ton more since.

 

[Scott z]

If it is just a drain, it still seems the proper procedure calls for plugging it prior to driving into high water. I've located mine and there is a spare bolt (the plug) located right next to the hole as described in the manual.

I'm still curious as to the specifics of what's inside. As I understand it, as the transmission oil gets hot and expands it has the ability to overflow out of the top mounted breather hole. I don't understand what fluids would drain from the bell housing drain. I'm still pondering my original questions:

Would plugging it for a full day (or permanently for that matter) cause damage? Sounds like a pita if your driving in the rain, encounter high water and then need to get out, lay on the wet ground and move this bolt plug. (And that's "bolt" not "butt") Once complete, how long can you drive with it plugged?

Whats it it really for?

 

[simp5782]

Its plugged so that water cant get up into the bellhousing and get swashed around by the torque converter and past the torque converter seal and fill the transmission up. The m939s have the same thing on them. Its specifically says plug before fording. Otherwise it should be left open so any crud or oil can escape. If its plugged and the rear main or the front pump starts to leak you may never know. Water does not need to be in that area especially submerged.

Also helps with the lmtv you have a fan shut off on the dash for fording

Sent from my SM-G935P using Tapatalk

 

[coachgeo]

Besides..... fording is not JUST an issue with water. There is sand, and other things stirred up in the water that would not be good for the Tranny that could be introduced thru that drain hole.

 

[Awesomeness]

If it is just a drain, it still seems the proper procedure calls for plugging it prior to driving into high water. I've located mine and there is a spare bolt (the plug) located right next to the hole as described in the manual.

I'm still curious as to the specifics of what's inside. As I understand it, as the transmission oil gets hot and expands it has the ability to overflow out of the top mounted breather hole. I don't understand what fluids would drain from the bell housing drain. I'm still pondering my original questions:

Would plugging it for a full day (or permanently for that matter) cause damage? Sounds like a pita if your driving in the rain, encounter high water and then need to get out, lay on the wet ground and move this bolt plug. (And that's "bolt" not "butt") Once complete, how long can you drive with it plugged?

Whats it it really for?

I've wondered the same thing, and can't think of any mechanical reason it couldn't be plugged all the time. However, I trust that the engineers that put it there did so for a reason, so I kept thinking.

What I came up with (purely logical speculation) was that it wasn't about a mechanical issue, but a preventative maintenance one. If it were plugged, and you had a leaking rear main seal on the engine or front seal on the transmission, it would fill with lubricant and you would never know. This is one of the only parts on the truck where you have an enclosed space that is not normally/intentionally filled with fluid, but could become so if a seal failed somewhere adjacent.

I'm open to hear any other theories.

 

[Scott z]

Thanks all. Makes sense now and confirms that we can easily plug the bell housing for a fair amount of time.