Transmission Woes - Help!!!! - URGENT

Hello Forum
 
I am pulling my Hair out trying to figure out what is wrong with my Car - I will start by a short history then the Symptoms.
 
**HISTORY**
 
Approx 4 weeks ago, I noticed some juddering whilst enagaging into Drive, so I took it to my dealers, and they told me that I had water contamination in my Transmission.  They recommended a Filter and Fluid change.
 
Approx 100 Miles after the above change, I lost gears totally (Can rev whilst in Drive) - So I had the Car towed back to the Dealer, who again said that a Filter and Fluid change would be advisable, as some contamination would have been left in the Torque converter.  At this point I declined. I decided that I will do this myself, So I air blasted the pipes after removing sump - and lots of gunk came out - Put a new Filter and Fluids - it ran nice for 300 Miles and then again died (same problem as above)
 
Spoke to a Transmission Specialist, who said that once Water had contaminated these boxes, it is time for a rebuild as the water dissintegrates some sort of Band or Clutch (cant remember), however he also said he had a Box from a 21K car, with Torque Converter.  So I chose the replacement option. - I was there when they removed my old box!!!
 
HOWEVER - guess what - it died on me again.
 
**SYMPTOMS**
 
I get a whizzing sound in a all modes (P R N and D, in S and C), however the weird thing is that if switch the car off, and start after 5 mins, I get gears for about 5 seconds then gone again! - Occasionally I would start the car , and it takes a few seconds to get into gear (almost trying to build pressure).
 
I have put on STAR - all Modules OK (EGS, and ETC)
 
NOW I am lost for thoughts, and would really like some pointers........
 
PLEASE Any Advice!!!!!

Year? Model? Mileage? You may get more responses if you place your question for a specific class. I'm having some transmission issues with my '99 E320 and happened to stumble on your post while looking for an answer to my problem. Good luck! 

water in transmission fluid normally caused by gearbox oil cooler leaking damaging gearbox