Heat marks on Birfs normal?

[HDJdreams]

Pulling my front axle apart on my 97 with 250k, which had been supposedly serviced few times but this is the first time I have been in it.

The first thing I noticed was the knuckle was full of “birf soup” (gear lube and grease), so my seals are shot. They were getting replaced anyway.

What concerns me is the heat marks on the birf joint where each of the 6 ball bearings are. Is that normal? Are they toast?

I only had the faintest of clicking on corners, I was hoping to repack them and swap sides.

 

[Tools R Us]

Normal, from machining.

 

[goranvolvo]

it is leftover from heat treatment

 

[Malleus]

EDIT:
OK, I take that back. The OEM Birfields I've seen don't have the heat marks on them, but some aftermarket forgings do:

So it looks like the manufacturer has elected to spot heat treat the wear areas; very cheap manufacturing decision. I'd expect these to crack under load around those hard spots. Eventually. This, IMHO, is why you'd want to heat treat them though and through.
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I have to disagree here. I haven't seen every Birfield made, but I'd bet these are induction hardened, which means the hardening has been done evenly around the circumference. I'd like to see a photo of the inside/outside. I'll bet those marks line up with balls that were stuck and annealed the forging through to the outer casing as they spun in place.

Having said that, I'd have no problem using them, but this isn't an artifact from the manufacturing process.

 

[HDJdreams]

Marks definitely line up with the balls.

 

[gummycarbs]

Pretty sure that my originals (~250k miles) look like that, as do the ~100k mile ones I swapped in. Oddly, I don't photographic proof.

 

[-Spike-]

EDIT:
OK, I take that back. The OEM Birfields I've seen don't have the heat marks on them, but some aftermarket forgings do:
View attachment 1627140
So it looks like the manufacturer has elected to spot heat treat the wear areas; very cheap manufacturing decision. I'd expect these to crack under load around those hard spots. Eventually.

I have to disagree here. I haven't seen every Birfield made, but I'd bet these are induction hardened, which means the hardening has been done evenly around the circumference. I'd like to see a photo of the inside/outside. I'll bet those marks line up with balls that were stuck and annealed the forging through to the outer casing as they spun in place.

Having said that, I'd have no problem using them, but this isn't an artifact from the manufacturing process.

Every birf I've seen, OEM or aftermarket, is discolored. It is not from friction related in any way to the balls. The balls are never discolored, and if they were mistreated enough to cause the bell to heat up enough to change color they would certainly show evidence of this. Like they'd be melted. They are never even scratched. The marks are most assuredly from the manufacturing process.

 

[HDJdreams]

What about the chips below the balls? Present under all 6, but vary in size.

 

[Malleus]

Chips? on the inner cage?

 

[Malleus]

Every birf I've seen, OEM or aftermarket, is discolored. It is not from friction related in any way to the balls. The balls are never discolored, and if they were mistreated enough to cause the bell to heat up enough to change color they would certainly show evidence of this. Like they'd be melted. They are never even scratched. The marks are most assuredly from the manufacturing process.

The balls should be significantly harder than the cages. This is common bearing design practice. The only way I've ever seen bearing balls deform/fail is if they've been overheated to the point where they've softened, or if something harder than them got in between them and the cage.

 

[Malleus]

My guess is these are soft:

 

[HDJdreams]

Chips on the inner cage below the balls.

 

[Malleus]

These are both listed for my '95:
This one comes with an OEM box:

and this one's from some fine German outfit:

 

[Malleus]

So it looks like you can get Outer shafts with or without marks, as you like.

 

[Malleus]

Chips on the inner cage below the balls.

I can't see them in your photos, but if they are regularly shaped, that is, they give you the impression they have been created by a round spinning tool, they're OK. A failed inner cage will break along microstructure fault lines, and will be ragged and asymmetrical.

 

[Tools R Us]

Every factory birf that I have seen has those marks, including new from the dealer, ~$500ea ones.

 

[Sean80]

These are both listed for my '95:
This one comes with an OEM box:
View attachment 1627159
and this one's from some fine German outfit:
View attachment 1627165

Where did you order them from? I need a new one.

 

[-Spike-]

Here's some pics of an OEM birf that was clicking. Notice that the discoloration is only on the outside. Probably because it happened during the machining process when they rough cut the grooves for the balls, and then they polished the heat marks out of the inside with the finish machining. There is also significant discoloration around the inside rim, which would be difficult to attribute to ball friction.

Here's a gratuitous pic of the cage, no chips. Those would concern me a little, as I expected to see them on mine since it was clicking a little. Not much though, maybe that's something that happens with long abuse.

 

[Malleus]

That second photo is what I expected to see. That is consistent with an induction hardening process. They stick a plug into the bore and heat the forging. The bearing surfaces are then hard cut to match the ball profile.

Looking at the end-on photo, I can see that the material is thin enough to have burned through to the OD. Good info to have.

 

[Malleus]

Where did you order them from? I need a new one.

I didn't mean that those are ones I'd bought, just that they were the specific ones listed for mine. I stole those photos from PartSouq; they have the best part photos

OEM outer shafts are available from Mr. T, for a very great investment; common wisdom (@cruiserdan and @beno) is to buy aftermarket and save your money. Just don't buy Chromoly or 4340 if you don't intend to wheel on soft trails. Pavement eats those up.