HYDRA-MATIC 6L50 (MYB), 6L80 (MYC) and 6L90 (MYD) Rear Wheel Drive Automatic Transmission Control Valve Body Assembly Reconditioning

The information outlined in this bulletin is designed to provide easy to follow control valve body reconditioning instructions using the new illustrations to simplify reassembly of the 6L50, 6L80 and/or 6L90 automatic transmission control valve body assembly.

Caution:  Valve springs can be tightly compressed. Use care when removing retainers and plugs. Personal injury could result.

Notice:  After cleaning the transmission components, allow to air dry. Do not use cloth or paper towels in order to dry any transmission components. Lint from the towels can cause component failure.

Notice:  Do not reuse cleaning solvents. Previously used solvents may deposit sediment, which may damage the component.

Inspection Procedure for Shift Concerns

1. Using the exploded view, inspect each bore for freedom of valve(s) movement and evidence of debris. Pay particular attention to those valves related to the customer’s concern. IF VALVE BODY CLEANING IS NOT REQUIRED, DO NOT DISASSEMBLE THE BORES UNLESS IT IS NECESSARY TO VERIFY MOVEMENT.
2. Verify movement of the valves in their normal installed position. Valves may become restricted during removal or installation. This is normal due to small tolerances between the valves and bores.
3. If a valve is restricted and cannot be corrected by cleaning the valve and bore, replace the valve body. Describe the restricted valve on the repair order.

Disassembly/Reassembly for Cleaning Debris

1. If a valve is restricted by a metal burr from machining that bore, remove the valve and burr. Inspect the movement in the valve’s normal position. If no other debris or restrictions are found, reassemble the valve body and install in the transmission.
2. If the valve body has been contaminated with debris from another transmission component failure, disassemble all bores for complete cleaning of all valve body components. Keeping individual bore parts separated will make reassembly easier. Use the following illustrations for positive identification and location of individual parts.
3. Using GM Brake Clean, or equivalent, in a safe and clean environment (clean aluminum pan), clean the valve body and dry it with compressed air. Use appropriate eye protection.
4. Clean individual valve body components with GM Brake Clean, or equivalent. Coat each valve with clean ATF and reassemble in each bore. Check each valve for free movement during assembly of each bore.

Important: Position the valve body as shown in the following illustrations for positive identification and location of individual parts.