BURNED 3-4 CLUTCH/HI 2-3 SHIFT 700-R4 TRANSMISSION

1982-85 LIGHT DUTY WITH THM 700-R4 AUTOMATIC TRANSMISSION

This bulletin cancels and supersedes 84-B-78 (June, 1984), All copies of which should be destroyed.

Starting production of all 1985 THM 00-R4 transmissions, an air bleed orifice cup plug was added to the input clutch housing (Figure No. 3). Due to this change, the procedure listed below for air checking the 3-4 clutch piston and the check ball has been revised.

Some 1982-84 THM 700-R4 transmissions may exhibit a burned 3-4 clutch and/or high 2-3 shifts. (The high 2-3 shifts are experienced on C, K, and G truck gas/diesel applications only.)

Starting January 15, 1984, (Julian date 015), all THM 700-R4 transmissions are being built with a revised input housing and shaft assembly and control valve body assembly. Refer to Figures No. 7 and No. 8 for Julian date location.

The former input housing and shaft assembly had a check ball seat drilled into the housing. A check ball was installed into this hole and the opening was then staked to retain the ball (Figure No.1).

The revised input housing and shaft assembly has a check valve retainer and ball assembly which is pressed into the housing (Figure No. 2). For 1985, an air bleed orifice cup plug was added to the revised input clutch housing (Figure No. 3).

Only the revised input housing and shaft assembly is available for service. Refer to the parts manual for correct part numbers and model application.

Also, for the Burned 3-4 Clutch, air check the 3rd and 4th Clutch Piston and the check ball in the Input Clutch Housing for leaks by following the procedure as listed below:

1. If you have an input clutch housing which does not have the new air bleed orifice cup plug (Figure No. 2), place your thumb firmly over the oil hole on the turbine shaft shown in Figure No. 4.

2. If you have an input clutch housing which has the new air bleed orifice cup plug (Figure No. 3), place your middle finger over the air bleed orifice cup plug and your index finger over the oil hole on the turbine shaft as shown in Figure No. 5.

3. Place the nozzle of an air gun over the check valve hole as shown in Figures No. 4 and No. 5.

4. Inject a short blast of air into the check valve hole.

5. After injecting the air into the check valve hole, release your thumb or finger off the oil hole on the turbine shaft. At this time you should hear air escape.

6. If you do not hear air escape from the oil hole, remove the third and fourth dutch piston assembly and inspect it for damage. Also, check the check ball for proper sealing. If you hear air escape from the oil hole, the Piston Assembly and the check valve are good.

The new control valve body assembly is for the Burned 3-4 Clutch and the high 2-3 shifts which are experienced on the C, K, and G trucks gas/diesel applications only. The new control valve body assembly is identified with an "X" on the casting (Figure No. 8) to distinguish it from the past control valve body assembly.

Only the new control valve body assembly is available for service. Refer to the parts manual for correct part numbers and model applications.

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.