The 2004R transmission might not be the worst transmission GM ever built, but it's in a close race to the bottom with the Roto-Hydramatic. It's an overly complicated modification of another piece of driveline excrement called the 200 Metric. There are some excellent reference sources on the geometry and setup of 700 R4 TV cable linkage in non-OEM applications. It's difficult, but not impossible to make the TV system work right. Stay far away from early production examples of the 700 which had chronic problems with the torque converter lockup clutch failing to release when the vehicle stopped, causing the engine to stall.
Jerry
