Lost 2. Gear 97 4x4 Tahoe / 4L60E

I have a 97 4x4 Tahoe here in Germany with a rebuilt Trasmission that only have 15000 Miles on it , from one Day to the next Day the 2. Gear was gone. Everythinge else is pretty normal, The OD works, the1.Gear,the 3.Gear, and the Revers everything is ok. So i bring it back to the Tranny Shop to fix it, they start to drain the Oil, it looks and smell Ok, no Metall Parts in the Oilpan. They conect a Computer to the Data Link Conector and they found nothing, they put the Tranny apart an check every Valve and everything what they could took apart. But they found nothing, they told me that erverything from the Mechanicle Side is ok. I would say in my own Words they have reached the End of her knowledge.The last Phonecall we have they told me that mabe the Torque Converter is the Problem, but i dont think so. To explain my Problem here in Germany you dont have so manny Tranny Experts like you in the States, i have to mad a 150 mls Trip to this Shop. It is like youve bin in Luckenbach / TX an you are looking for a Volkswagen Dealer to explain My Problem a little bit.
So i be very Thankfull to anny Tip ore Information you can give me. And sorry for my poor English

So I take it that it shifts from 1st to 3rd (skips 2nd)?

Yes it skip the 2. Gear and goes straight into the 3.

Heat is the worst thing for a transmission.  A bad torque converter can really heat up the fluid and that can cause damage to the transmission.  That would explain why the fluid looks and smells bad. 

It sounds as though the smell and color are both fine

You're right, I read that wrong.