The Great TV Mystery
Part Two: TV feed fluid
The purpose of Part two is explain where the TV feed fluid is directed to once it enters the TV feed passage. Once explained, it will become clear that these transmissions need a TV system that buries the TV plunger inside the TV bushing at W.O.T.and positions the TV valve at the correct position inside the TV bushing at idle!
This graphic is a reasonably accurate representation of a Th-700R4 Throttle Valve (TV) system in the correctly set factory position for a Chevrolet C/K pick up with a 350 CI engine with TBI
Quoting GM again, not to be redundant, but to again focus our attention on the functions controlled by the TV cable system!
"The TV cable used with the 4L60 transmission should not be thought of an automatic downshift cable. The TV cable used on the 4L60 controls line pressure, shift points, shift feel, part throttle downshifts and the detent downshifts. The function of the (TV) cable is similar to the combined functions of a vacuum modulator and a detent cable."
The five activities listed above are influenced by the TV valve movement. As the TV Valve starts feeding TV fluid into the feed orifice (blue circle), it's directed to three places as it enters the passage shown below (area shown in transparent red). TV fluid passes through the spacer plate (green circle in bottom picture) into the transmissions pressure boost circuit where it instantly boosts line pressure. This fluid also feeds to the circuits that control up shift timing and feel called MTV. The transparent red fluid also feeds the port shown (purple circle in top picture) directing TV fluid back into the TV bushing and TV plunger (See heavy throttle upshift and downshift control section below) to assist plunger movement so the pedal pressure isn't excessive. This fluid also feeds the part throttle (Green arrow) and detent (Yellow arrow) ports in the TV bushing.
The picture below has a hole (Green circle with explanation in the spacer plate TV fluid flows through after entering the passage in the valve body indicated with the transparent red color in the picture above. This fluid
There are plenty of "cross over" effects between these three circuits which we will not even attempt to explain since this article is only meant to provide an overview of the TV System and its effect on these transmissions. When you read the following few paragraphs, it should become clear that all activities of these transmissions are effected by the TV valve system. The following information is offered to help the owner / installer understand why the TV valve must have a correct starting (idle) position and a correct wide throttle position, not just one or the other. By the end of Part Two it should be obvious that some aspect of the transmission management will not be correct unless the TV system is managed correctly through its full spectrum of movement!
The TV feed fluid is directed into three control circuits which subsequently control or effect the following:
LINE PRESSURE MANAGEMENT
Line pressure management and upshift and downshift timing and feel are fed directly as fluid enters the feed orifice above.
UPSHIFT AND DOWNSHIFT TIMING AND FEEL