TH is the shortcut for Turbo-Hydramatic.
You can found more informations about the TH Family on wikipedia US.
http://en.wikipedia.org/wiki/Turbo-Hydramatic
I will advise to study the book "Haynes TechBook - General Motors Automatic Transmission Overhaul" and the Workshop Manual from Bentley and Rolls-Royce.
It is available under the URL :
http://depositfiles.com/de/files/84fzdbf41
http://depositfiles.com/de/files/84fzdbf41
- The Rolls-Royce Silver Cloud I and the Rolls-Royce Silver Shadow with the 6.2 engine use the GM TH 400 Transmission
- The Rolls-Royce Silver Shadow with the 6.75 engine use the GM TH 350 Transmission