INPUT HOUSING ASSEM THM 700-R4 AIR CHECK OIL PASSAGES

When disassembling a THM 700-R4 transmission, it is a good idea to air check the oil passages in the input housing assembly.

Air checking these passages will help you diagnose:

1. Block channels 2. Cross channel leaks 3. Clutches are or are not applying 4. Checkballs are or are not sealing

After the input housing assembly is removed from the transmission, perform an air check as follows:

1. Adjust air pressure to approximately 30 psi.

2. Blow air into the hole nearest the end of the turbine shaft (hole marked #1 in Figure A).

(Figure A shows the input housing as installed in the transmission. However, these checks are made with the input housing assembly removed.)

Air blown into hole #1 will exit out the end of the turbine shaft around the checkball capsule. (Use care not to blow transmission fluid on your clothing or body.)

3. Now blow air into the hole marked #2. This is the overrun clutch passage. The air from this passage will go past the lip seals on the forward clutch piston and exit through hole #3 on the turbine shaft. If you place a finger over hole #3, to block the air flow, the overrun clutch should apply.

4. Now air check hole #3. This hole should apply the forward clutch.

5. Air checking hole #4 should apply the 3-4 clutch.

6. The last hole on the turbine shaft is for lube supply to the internal components located along the output shaft. Any air blown into this hole should exit out of the one hole at the back of the turbine shaft which does not contain a sealing ball.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.