Differentials - Front & Rear

Driving offroad should involve a deeper knowledge and understanding of your vehicle. For example, while a tall, 4WD vehicle can go many places including through water, it's very helpful to know the vehicle's limitations such as the fording depth which is determined by the lowest "weak link".

The depth a vehicle can ford water is determined by things like breather tubes on the differentials, transmission, transfer case (if applicable), door seals, etc. On some vehicles designed for deeper water passage the weak link can be the air intake which is often why you'll see some offroad vehicles with snorkels installed as these raise the intake height considerably.

This thread is for a discussion of the front and rear differentials, their maintenance and ways to extend the breather tubes to a higher point on the vehicle in order to protect against water ingestion.

From the Raptor SVT 2010 Owner's Guide Supplement, page 23:

"Refill Capacities"

Front axle lubricant: Motorcraft 80W90; 1.7L (3.6 pints)

Rear axle lubricant: Motorcraft SAE 75W-140 Rear Synthetic Axle Lubricant; 2.6L (5.5 pints)

From page 24:

"Your vehicle's rear axle is filled with a synthetic rear axle lubricant and is considered lubricated for life. These lubricants do not need to be checked or changed unless a leak is suspected, service is required or the axle assembly has been submerged in water. The axle lubricant should be changed any time the rear axle has been submerged in water".

Note that it does not say how deep the water needs to be to "submerge the axle" so, taking it literally, the axle would have to be submerged below the top of the pumpkin.

While I'm here, here's some others:

Transfer case lubricant: MCXL12; 1.4 - 1.5 L (2.9 - 3.1 pints)

Transmission fluid: Motorcraft Mercon LV ATF 12.4L (13.1 quarts)

Driving through deep water is addressed in the 2010 F-150 Owner's Guide on the following pages:

312 - "Driving through deep water may damage the transmission.

If the front or rear axle is submerged in water, the axle lubricant should be replaced.

314 - "Driving through water

If driving through deep or standing water is unavoidable, proceed very slowly especially when the depth is not known. never drive through water that is higher than the bottom of the wheel rims (for cars) or the bottom of the hubs for trucks.

When driving through water, traction or brake capability may be limited. Also, water may enter your engine's air intake and severely damage your engine or your vehicle may stall. Driving through deep water where the transmission vent tube is submerged may allow water into the transmission and cause internal damage."

Note: above bold text is from the manual.

Unfortunately, the manual doesn't tell us the height of the transmission vent tube.

GREAT point Dan!!!!

I know someone who, on their FJ Cruiser, installed the remote vents similar to what Junior posted here that he did to his FJ. Then they went into some deep water and it got into the auto transmission! (the vent is cast into the top of the trans someplace... no vent tube or hose attached).

Of course he didn't realize this at first so by the time he did, Toyota said the transmission was "junk" and not covered by warranty. (and I don't blame Toyota for making that call)

An exchange transmission and a few thousand dollars later... well, you get the idea!

So where is the transmission vent on the Raptor? Could a vent hose be added/extended by those who wish to risk crossing deep water?

Well, if I did this right here is the pic of the 6R80 I had out of a 09' F-150 and you can see the vent on top of the transmission just above the cooler line connections and just to the right of the top of the bell housing area.



The vent is a metal type with an integral "floating" cap. It is pressed into the case and I am sure it could be altered to add an extension, however quite difficult with the trans assembly in the truck.

FSM

Thanks for the pic.

I seriously doubt that the water crossing in Mojave entered the trans breather.

We would have had water coming thru the A/C vents (joke).....seriously would have had water up to the doors, which we didn't.

I am going to be doing a F + R diff flush sometime this week/weekend (was supposed to do it today but was in lazy ass sloth couch potato mode today)

I bought all the materials today.

Thanks FSM!!!

You'd have to get pretty into some pretty deep water to submerge that vent but if I wanted or needed to cross deep water with any regularity that's the vent I'd worry the most about raising...

(Personally, I avoid water crossings unless they are very shallow... but sometimes you don't have a choice)

I looked at the rear differential breather yesterday. I'll take pictures of it but as I recall the breather is in the back of the axle (not on top) on the right side. And the breather tube runs up to the bottom of a cross member underneath the bed of the truck. It looks to vent into the cross member which seems to be as good a location as Ford could have easily put it.

My concern is these cross members get flushed/rinsed out if you're cleaning your Raptor after running it in the desert/dirt. Is it likely that this water will go into the breather tube?

On a related note, I would be a lot happier if Ford put some dimensions on the three breather tubes (front and rear differentials and the transmission breather). I understand why they didn't (don't want to commit to a water fording depth as a "guarantee") but they're dimensions I think we offroaders absolutely should have.

As Mark says, "sometimes you don't have a choice" (other than possibly choosing to turn back, retreating in the direction you came from which often isn't at all practical).

Wasn’t there an Amsoil fluid spec post?
I’m searching .....

I have crossed many rivers and streams in my former Jeep JKUR with a snorkel and extended breather tubes for the diffs. Changed the diff gear oil every spring and never found any water in the diffs, and we often high pressure wash the underside after Mojave. Crossing Rubicon Springs would get pretty deep at different times of the yer as well. I never found water in the auto trans either.
The Jeep cant be better at this stuff unless Ford just never presumed the trucks would be taken WAY off road.
Can't do the Rubicon in our trucks but sure wish we could, too narrow a road.