Cracked Front Diff Housing

[SRHAGEN]

You got a good one.

At some point we might see documentation from Ford, similar to what finally was released regarding the floating axle bolts, and it will fence by date of manufacture as well as Dearborn VS KC or both.
[last week I pulled a c3500 loaded dump truck out of the mud with my truck using 4 low and the elec locker. My front wheels were on black top. Not a great feet actually. Forward tow. .

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[SRHAGEN]

I think you were right the first time.

The types and locations of the failures, seem too different to be a design flaw.

Leads to material, or maybe, casting process.

I hope mine holds up , because I’m using it like every other 4x4 I’ve owned, for Everything it’s got. If it breaks I won’t buy another ford until it’s resolved.
I Really like that 32 valve V8.

 

[Big Dog Daddy]

Rubbermount for vibration dampening causes flex in many different ways. A solid mount can’t move around. Just a guess.

The mounting of the differential carrier, whether isolated through flexible mounting or rigidly mounted should not make a difference, assuming all of the flexible mounts stop at the same point relationship to each other when full torque is being applied to the gear case.

The gear case has to be able to withstand its full design torque without any distortion to it's internals due to the torque being transmitted through it. If any distortion happens to the housing this will result in gear misalignment and bearings losing their adjustment, and will destroy the gear case very quickly.

Put another way, the rear axle on an f150 is mounted on leaf springs, a completely flexible mount. But under heavy acceleration, the axle housing will and wind up the leafs as torque is applied from drive shaft until forward motion is achieved. Once in motion a equilibrium is achieved between the input torque to differential and output to the wheels. At this point the leaf springs basically flatten out again but they are still being used as a torque arm to transmit power to the wheels.

 

[Gros Ventre]

I've taken down and swapped the front differential on a GMC. It is mounted with resilient mounts, but they are rather stiff. I suspect that's to keep alignment. Haven't taken down my F-150's front. I'd expect it to be mounted similarly, aren't they mounted to the frame that way?

 

[Snakebitten]

The VAS brace adds a second axis support against the twisting of the differential. It bolts to a casting hole that's there, but not used?

 

[DcnPat]

Th
Thank you for the advice. The dealership told me that it was Ford Customer Service and not them and that the dealership was working to get Customer Service to change their minds about the not covering the warranty. I didn't find out until after the truck was repaired at my expense that the service manger and the owner of the dealership were in agreement with Customer Service. They lied to me from the beginning, had I known I would have absolutely taken it to another dealership.

Always get the replaced parts if it is repaired at your expense. Pretty sure they have to give them to you if you ask when you pick up the vehicle. That way you have at least a bit of proof if you later dispute the warranty denial. (Plus it's fun to watch them squirm if they "already disposed" of the parts.)

 

[JBHBILL]

Always get the replaced parts if it is repaired at your expense. Pretty sure they have to give them to you if you ask when you pick up the vehicle. That way you have at least a bit of proof if you later dispute the warranty denial. (Plus it's fun to watch them squirm if they "already disposed" of the parts.)

I should have thought of that. I have pictures but of course there's no guarantee their from my truck.

 

[Gros Ventre]

Well, they re supposed to make the old parts available to you... without being asked... That mounting method for the front differential seems to only provide a two axes of support. Given the failures we're seeing I'd bet the cracks can be traced to third axis flexing. I suppose that Ford thinks the resilient mounts are stiff enough for third axis support. Given the failures seen, I'd say that third axis flex, if you really torque the differential, just doesn't get the support needed.

 

[Snakebitten]

I'm just happy that Ford casts that other mounting point, although it's strange that it's not used.
The kid in Houston (VAS) came up with a simple and well thought out method for leveraging it. (I drove to Houston a few years ago and met him and got to see his fabrication shop)
His product(s) are well known in the performance crowd. The guys that are chasing ET's with their F150.

I'm personally not a Boost Launcher, but I am known to roll-into smooooothly a max torque 4A short term event when I get the calling. I felt better knowing that the front differential wasn't hanging in the wind so much.

It's inexpensive enough, although I did have to cut a slot in the skid-plate to accommodate the portion of the brace that protruded below the skid plate plane. I think the hottrodders just leave it off.

 

[Gros Ventre]

So how rigid is the propeller shaft between the transfer case and the differential? If it's rigid, lengthwise, then Ford thinks that covers the third axis. I think Ford put that ear in the design planning on using it for that axis. Then changed something else in the design to cover that... probably in chasing weight reduction...

 

[Snakebitten]

Don't know.
But as stated earlier, the boost launching wheel-hop is eliminated with the brace.

So there must be some torque induced movement that can be reduced/eliminated if the owner feels like it might benefit?

 

[powerboatr]

Don't know.
But as stated earlier, the boost launching wheel-hop is eliminated with the brace.

So there must be some torque induced movement that can be reduced/eliminated if the owner feels like it might benefit?

really wondering how wheel hop is stopped or reduced using that brace?
lower control arm, spindle, strut and upper should be holding wheel in place.
so this means we have some pretty heavy torque twist going on to tweak the front mount and frame area
maybe a sideways load up.
we need a go pro video
before and after

 

[Snakebitten]

Similar to getting wheel hop in the rear if you apply enough torque to get axle wrap?
Or why traction bars prohibit it?

VAS traction bars are another device the same customers will install.

 

[Gros Ventre]

really wondering how wheel hop is stopped or reduced using that brace?
lower control arm, spindle, strut and upper should be holding wheel in place.
so this means we have some pretty heavy torque twist going on to tweak the front mount and frame area
maybe a sideways load up.
we need a go pro video
before and after

If the picture above of the mounting resilient mounts is accurate in that those two are the only mounts or suspension points, then a real whopper of a load imposed suddenly, would wrap the casing along the axis of the two wheel shafts. Not good. In turn this could crack the casing. Go look at the cracks and see if they could be imposed by such a wrapping motion along the axis of the wheel shafts. If a crack starts, it then propagates (and is very difficult to stop) because the stresses are concentrated at the head of the crack which is a point loading.

 

[Snakebitten]

This is a screenshot of Ford Techmacoloco Brian showing how to change the differencial fluid.
The unused hole in the casting of the axle tube is there in all its unmarred glory.

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