Zinc in Automatic Transmission Fluid

Maybe my info is out of date, but vitually all ATFs were base on Zinc(ZDDP), and levels would be well in excess of 100ppm.
(TASA, Dexron, Mercon, CAT TO2,Allison C4 etc)
It may be that this particular Voith transmission requires a none zinc type fluid and you will see this from the lubs recommendation list, which should not contain any of the above spec products. I would have thought that Voith would stress this if it is so important.
Under very high temperature zinc additives can become very corrosive and may change the frictional properties required by the transmission.(past involvment in lubricants for Voith and ZF products in the UK rail and bus industry)
What is the level of phosporus?

Phosporus is at 200-400 ppm on virgin oil. What baffles me is how Zinc spikes up to 600ppm while phosporus remain the same in a sample from some failed trans. On other failed trans P & Zn remain at virgin levels while iron spikes appear on all of them (>400ppm). These are new transmissions equipped on new buses with less than 100K miles. Lets say, we have sabotage - If an engine oil with P=1500ppm and Zn=1500ppm is mixed with ATF in the middle of the ATF life, wouldn't P go up as well with Zn at the end? I will meet with the ATF reps this afternoon. I will keep you posted.

Briefly checked Voith recommendations on the net and North America has a different list to Europe(Don't know the signifcance of this).
As you rightly say any contamination with ZDDP type product would mean Zinc and phosphorus present in ratios approx 1:1
Spiked Zinc levels suggest wear of a component as do Fe spikes.

Could please you send me those links to both recommendations.
I have met with the ATF supplier and Voith reps and really discussed this matter. The supplier took the intitiative to deliver their products in their own tankers to bypass their distributors where they believe the contamination occured. Voith on the otherhand said that this little zinc is reacting with brass bushings inside the transmission causing it to fail. Suddenly, his following jargon became muffled to me. I just stared at my superiors to see if they were buying this bullsh**. How could zinc be bad for brass when brass is composed of zinc.

Suggest you google voith H55.633635 for none- North American list.
Just for information Zinc in the oil likely to be in the form ZDDP, containing sulphur.It is the sulphur and elevated temperatures that cause the corrosion.
If Zn ~100ppm and P~300ppm, then if the oil should be Zn free, there is considerable contamination of say ~10% engine oil which would increase the viscosity and show other elements such as Calcium ,boron or magnesium present(some may be present anyway in the ATF)
You might ask your lube supplier what type of antiwear is used, if any in the ATF?
From you remarks it looks like your supplier may have contaminated the oil.
You could take a sample of your new engine oil and the uncontaminated ATF and get them analysed to see what's in them, which might elliminate your side from guilt.(or not!!)