Needless to say I was more than thrilled after busting into my core trans to see all the gears looked new: teeth, synchros, bands etc. However I noticed metal hair (flake) on the magnetic drain plug and couldn't find out where it came from until I saw this. Looks like stress cracks of some sort on the pinion and one chip. Is any of this salvageable or are my pinion and ring junk? How does this even happen?
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I saw a pinion gear that looked like that once. Except, it was missing a tooth and one other tooth was close to breaking off. The teeth that were still attached had significant galling like your first picture--but much more of it.

Dave Ferguson asked me what I saw there. He declared, with that trademark grin of his, that it was "Proof that my motor makes enough torque!"

That R&P may have been abused in the past.

--DD

No. The main issue is that of weakness or noise. The location and since it is a single divvit, weakness not a likely issue. If it was not making noise before then that is not an issue. If you dont know if it was making noise as you havent used it, it probably was not. I would run it in my car

Edit** I would run it behind a stock 4cyl. I would not run it if it is going into a more tq engine.

It's junk in my book, I'd guess you also have spalling on your ring gear also.
The carburized surface of the gear has broken out in that spot. This is often caused by improper backlash thru wear, lubrication lack or failure, bearing wear.....3 involved or mis-set pinion depth. It ain't gonna get any better. Take a close look at your ring gear...off with the side plate. If it looks good, they may last for a while.
I would guess the scratches on the tooth face you see are from the ultra hard bits of flake off metal passing thru on their way to your drain plug. All the bits prolly didn't go there and aren't doing the rest of the gears any good.

The other marks are normal wear on a pinion. The ring gear almost never gets roached. I have seen numerous pinions badly mangled with good looking rings.

However, I do sell good used R/P sets for cheap

Thanks for the updates, this was going to go in my V8 car, with F, fV, fN, fH or fHB. So I guess I'll have to break into my good trans I haven't pulled the ring gear yet but I'll call it a loss for my needs.

Hey doc, you have an 8:35 for cheap? I wish...Actually I only have enough saved for an H/HB gear at the moment.

Do not use that pinion in the V8

I have that 8:35 from a 930, I think. Stock 901 R/P from me are $50, but need to be set correctly

Hard to see, but here's a toasted ring and pinion set....





These are the carnage from my car. I did something to damage the Left differential bearing, or I got a bad bearing, and under load the bearing failed. It let the diff shift, and changed the backlash on the ring and pinion. That stripped teeth off both the pinion and ring gears. FYI.. this is not the first 914 transmission I ever overhauled, and I had the factory tools (borrowed from Zims) to setup the backlash when doing it.

If it were me, I would not use the one you have in my car. Even with perfect gears, one little mistake can have large consequences.

I have to agree, and wish add, once the gear surface starts to spall, it will continue to erode and contaminate
the oil with particulates. There will be a temporary plateau of erosion, at which time, temperature and friction will increase,
and that feature will fail, unable to cope with the load.
I would not run that, especially with a V8. I would talk to Dr. Evil, if I were you.
Replace it, and sleep better.
...worked on the stress analysis of H60 intermediate and main gearboxes, monitoring gear crack propagation during
destructive testing, using sensors that detected the onset of friction with 20k samples per second data collection.
Even tracked the progressive wear caused by misalignment and destructive particulates causing further spalling.
Gear crack propagation to root happens so fast, (milliseconds).
One second the load is equal on intermating gear surfaces, then one fails, causing an increased cyclic load
(worse condition than constant load) on adjacent teeth and catastrophic secondary failures follow very quickly after that.
...in a word...chunky...