This upgrade kit is for a common problem described in this article, for the Chevy 4L80E transmissions. It is designed to eliminate the cold start hesitation due to the transmission fluid draining back out of the torque converter after extended periods of non use. Below is a description of the problem in detail.
Automatic transmission systems of the this design have a hydraulic system which includes at least a hydraulic pump, a valve body having fluid conducting passages or circuits, input and exhaust ports formed within the fluid circuits, and a system of spool valves so-called because of their resemblance to sewing thread type spools. Such valves are comprised of cylindrical pistons having control diameters or spools formed thereon, which alternately open and close the ports to regulate the flow and pressure of automatic transmission fluid (ATF) within the fluid circuits to actuate various components of the transmission.
Pumps in automatic transmission systems are generally positive displacement pumps driven by the engine of the vehicle wherein the transmission is installed. A positive displacement pump is one, which has the same output per revolution regardless of pump or pressure already developed in the system. Thus, it is necessary to regulate ATF pressure so it does not get too high and damage other components. In the GM transmissions a pressure regulator valve employs a piston and a spring that compresses at a specific pressure to allow some ATF to flow back to the pump reservoir or sump bypassing the hydraulic circuit and reducing pressure. By using a pressure regulator valve with a compression spring calibrated to a pressure lower than the pumps output, a constant ATF pressure can be maintained in the hydraulic system during operation.
When the engine of the vehicle is turned off, ATF contained within the torque converter during operation gradually drains back to the fluid sump. At initial engine start-up this can result in an insufficient fluid level in the torque converter to operate the vehicle. In addition, the original equipment manufacture (OEM) pressure regulator valve in the GM transmissions does not send sufficient line pressure from the pump output circuit into the torque converter charge circuit inthe Park gear range or at idle speed to refill the torque converter to permit instant operation of the vehicle at engine start-up.
The cure is to produce a valve assembly that is machined out of better materials and seals better, thus eliminating the over night drain-back of ATF from the torque converter to the transmissions. This new designed valve successfully eliminates this problem. Several of the aftermarket suppliers offer an upgrade kit too. All produce positive results. Don’t buy a 4L80E transmission without the upgrades. GotTransmissions.com @ 1-888-344-8044.