Originally Posted by ASE Doc
Hi Guys, I've been doing a lot of research as I prepare to put my 700R4 back together. I read Tony's 700R4 pages and found some interesting points. One thing that Tony talks about is blocking the line bias valve. Apparently, the line bias valve bleeds off line pressure above 1/2 throttle. Blocking it prevents the bleed off and maintains higher line pressure which I would imagine produces faster firmer shifts. I am very interested in this since making sure that the 3-4 clutches don't slip and burn is of great importance to me. My question is, why did GM design this valve into the system to begin with? Is there any down side to disabling it?
One more question I have concerns the pressure regulator valve. My trans had the .500 boost valve already installed. It also had the regulator valve modified by grinding down the valve between line pressure and converter feed. This would create constant flow to the converter(clutch maybe) when it would have normally been closed off. What is the purpose of this? Does it increase flow through the cooler? Thanks in advance for any input.
Line bias valve operates as you mention. Why GM designed it that way? Ask GM engineers. You can block the line bias valve fully or install a stronger spring so main line pressure ramps up quicker & higher. A .471 main boost valve with .282 or .296 secondary boost valve with a blocked line bias valve works well on the street for main line pressure and proper TV linkage operation.
The mod to the main PR
valve does increase flow. GM cut notches on the PR
valve in later design changes