Yes have had higher stalls in other vehicles. We also revved it past 3000 just to make sure. grabs more with less rpm. If I had a level smooth driveway I think it would idle around like it should, slowly moving. As soon as you touch the throttle it stops and free rev slips with the whine. I have been researching this like crazy, and am still coming up short. I was sure it was the pump until I did the pressure test. The planets are standard angled ones too. I am stumped, to say the least. I thought maybe there is some massive leak somewhere in the valvebody, but the line pressure should be low if that was the case right? Also behaves the same in all shifted gears.

 

We tried it with the gear selector in all positions. It does it in 1st and reverse. I don't think I can try actual 2nd, 3rd, or 4th since I believe in 2,3,and 4 it starts out in 1st gear. Maybe there is a way to put it in 2nd with HP tuners in the diag section. I am not sure on that though.

 

It could be a converter. My issue is you said it slips forward and reverse two very different hydraulic circuits, But line pressure looks normal in both . No commonality exist between fwd and reverse in first gear position hydraulics and reverse , Nor any clutch applications. The OVERDRIVE sprag does have to hold in both so it's a possibility.
Right now reading over all you have posted and checked Im leaning towards either the converter or OD sprag not holding. More to the converter because in MANUAL 1 the overrun clutch should be on taking sprag out of the equation. You could try using scan tool to apply converter clutch this would effectively bypass the converter and see what you end up with. If you do lock converter with scan tool to test also have it in 2nd gear commanded.

 

So, I did some testing. Truck drives forward when commanding 2nd and with the converter clutch on. Did it in 3rd gear too. almost better in 3rd even. I thought with the tcc on it would die, but it acted like a normal trans starting in 2nd.
It is a brand-new Circle D billet converter. Hmmm. Sounds like a bad out-of-the-box converter eh?

 

Yes would tend to point to converter and a converter can cause whine. But if slipping stops with it locked then that is where I would go. Circle D is a good company and I am sure will work well with you on it.

 

can you post a copy of your current tune? I have had a couple customers this last year with mismatched OS segment swaps causing issues not totally different than what youre describing.

 

Did you ever find the issue?