i have a P0757 setting, what happens: i come to a stop when in D4, go to accelerate and the car doesnt move, i drop it into D1 manually and it goes, it will also shift into 2nd and 3rd manually. the first time this happened i dropped the pan, found some very small metallic particles in the fluid, cracked open the filter and found some larger ones. i replaced the filter, and the 2-3 solenoid(it was only $20) with the updated solenoid from GM with the screen, drove the car last night and it happened again. also the first time this happened the converter or pump was making alot of noise, almost like a loud "whiiiirrrrrrrrring" sound... i pulled over and shut the car off, checked the fluid and started it back up, checked the fluid again and the noise was gone - i went straight home(about 5 miles) and the trans acted fine.

here's some backround info:
trans was rebuilt about 3 months ago and has @1200 miles on it, has the upgraded sunshell/etc and clutches, bands... i recently put a new 4000 stall converter in(had a 3000stall before that) and had it dyno tuned(didnt drive it with the new converter except to get on and off the trailer). when i put the converter in i filled it before installing it, the fluid isnt burnt.

i called the guy who did the trans(whom ive dealt with him for almost 10 years now) and he thinks the new converter is bad, or the tune is causing it - but the debris in the filter bothers me(he did say if i pull it back out he'd go through it and make sure the trans is ok)

now i put 1100 miles on it before the new converter and tune and it didnt skip a beat so my gut feeling its one of those 2 variables - anybody have any ideas? could it possibly be the tune??? any help is greatly appreciated

here's a pic of what was in the filter:

 

I would have to concur with your builder seeing the metal that you very likely have a converter failure.
The PO757 is likely being cause by the 2-3 shift valve being stuck in the bore due to metal contamination
PerformaBuilt

 

i pulled both pieces of the valve out and cleaned them when i put the solenoid in, and also cleaned the bore(but i didnt remove the valvebody itself) but im guessing it got stuck again. thanks performabuilt for your response!

 

this might be occurring if you have a loose converter..delete the trans codes and you will be ok.

 

its tuned for the loose converter and actually gets stuck in 4th gear...