7.3L M275 failures/recalls?

Uuuggg, my head hurts! ?

Edit: BTW, I'm totally convinced this problem is 100% related to the high torque output of the 6.7 engine, and exacerbated by the 3.55 gears unique to those trucks. This set of parameters likely produces an excessive amount of twist in the axle tube between the differential and the hubs. With the tires planted firmly and accelerating hard, the weak link is revealed at the spring saddle plate connection on the axle. With substantial weight loaded on the springs from say a goose neck trailer, the springs are holding the mounting plate firmly in the plain of the springs and the axle tubes likely twist at the welds on the saddle plates, eventually fracturing the wall of the axle tubes.

I'm not completely sure the 3.55 gears make this worse, but again they are unique in these trucks to the 6.7 engine. It is possible that 4.30 gears in a 6.7 truck may even make the problem worse. If there are Super Duties being built with 6.7 engines and 4.30 gears this will become evident if it's a problem.
6.7 450's use the 4.30 ratio but it's only in the M300 differential.
 
6.7 450's use the 4.30 ratio but it's only in the M300 differential.
Ya, different axil on the heavier trucks. Again I'm not sure if the 3.55 gears are part of the problem or not, just that they are specified with the 6.7 in the 250 and 350 Tremors and for now the problem is limited to the diesels. Clearly the torque applied to the rear axil is high enough with this engine that it's twisting the axil housing tube enough to fatigue the welds at the spring saddle bracket.
 
Really not happy about this, wanted a 350 Tremor (to haul a truck camper) and had to settle for a 250 Tremor because of availability. Since the rear end was the same and only a sticker game, I was comfortable with my choice. Now really concern about this. Will haul a 2800lbs dry camper, will likely be at 4,000lbs once fully loaded.
 
Well, I've already towed about 7500 miles this year out of my 10k I have on my truck. Haven't noticed any issues, yet.

A camping trailer I presume?

I’m more concerned for the agricultural use case. Very dynamic tongue weights, not to mention legal allowance to overload.

Never imagined I’d have to worry about crushing an axle, of all things, in a Super Duty. And that Ford would just shrug at the problem!
 
A camping trailer I presume?

I’m more concerned for the agricultural use case. Very dynamic tongue weights, not to mention legal allowance to overload.

Never imagined I’d have to worry about crushing an axle, of all things, in a Super Duty. And that Ford would just shrug at the problem!
Jeep on bumper hitch car trailer, I'm not pushing the limits at all.

But I'm building a second jeep now and will go gooseneck with two jeeps next year so it'd be nice if my axle wasn't shit.
 
One theory is that paint flaking off the axle in that location is indicative of axle tube flex. Well - I have some flakes and they are only showing up under or very near the perches. Sounds legit, but the coatings are shit anyway you look at it, so who knows….
024AF29B-102B-4816-8E31-52832CF93BE8.jpeg
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One theory is that paint flaking off the axle in that location is indicative of axle tube flex. Well - I have some flakes and they are only showing up under or very near the perches. Sounds legit, but the coatings are shit anyway you look at it, so who knows….View attachment 29244View attachment 29245
Mine had that at 6 miles. I think it’s from lining it up on the chassis.
 
Does anyone think the driveshaft disconnect will be exacerbated by the 3 1/2” block on the 6.7L Tremors? The bigger the block, the more axle wrap when applying heavy loads of torque. I am towing a 9500 lb TT with a 1350 TW and I just got back from a 4200 mile round trip to Yellowstone. I had no problems going up and down the long 6-7% grades through CO, WY, ID and MO, but this thread has me wondering.

I swapped out my factory blocks for Deaver Progressive Add-a-Packs Leafs to minimize axle wrap and I am using AirLift 5000 lb Ultimate airbags, so I hope I am not affected by this issue. A quick look under my truck shows the same type of paint missing on the front of the axle as the previous post, but I am pretty sure that was there when I first got the truck. (mine has more paint missing right under the leaf springs on both sides)
 
It is my understanding that no, the axles on a 7.3L and 6.7L are not the exact same. The whole F250 Tremor is the exact same as a F350 is not true. Only an F250 Diesel Tremor has the same rear as an F350.

There is a thread, on these forums, that includes a video outlining the specifics. I believed they were the same as well, but it is not true.
It IS true...all Tremors are the same except for the 7.3 has a 2.5 inch hitch reciever and different front springs......that is it!

Capeesh!
 
One theory is that paint flaking off the axle in that location is indicative of axle tube flex. Well - I have some flakes and they are only showing up under or very near the perches. Sounds legit, but the coatings are shit anyway you look at it, so who knows….View attachment 29244View attachment 29245
It's possible. Mine had the missing paint when I brought it home (~8 miles on the ODO). I suppose the paint could flake off if the tubing became deformed when the nuts on the U-Bolts were being torqued down. Someone could verify this if the axle was unfastened for some reason (maybe when a lift kit was being installed?).
 
It IS true...all Tremors are the same except for the 7.3 has a 2.5 inch hitch reciever and different front springs......that is it!

Capeesh!

Thanks for the bandwagon response! I totally didn't own that in my own post where I corrected myself and I must have utterly ignored all the other responses, even those that included links to threads and videos exploring the issue.

It wasn't until I read your post, like four days after the fact, that really drove it home: I was wrong... So very very wrong.

I am currently investigating appropriate avenues of contrition.
 
Why does the 7.3 F350 have a rear gross axle rating of 6950lbs while the 6.7 F350 has a rear gross axle rating of 6830lbs?

The 7.3L weighs less so therefore can accept additional load. The heavier 6.7L has less available overhead due to it's weight and it's rating reflects that.
 
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