2-1 COASTDOWN CLUNK 200C SERVICE INFORMATION

MODEL AND YEAR: 1984 CAPRICE, IMPALA, MONTE CARLO, CHEVETTE 1985 CAPRICE, IMPALA, MONTE CARLO, CHEVETTE 1986 CAPRICE, MONTE CARLO 1984 S/T TRUCK WITH THM 200C 1986 EL CAMINO WITH THM 200C

Bulletin 86-197 is being reissued to correct the Part Number for the pressed on Rear Internal Gear listed on Page 2. All copies of 86-197 (Section 7A) dated Nov., 1986 should be destroyed.

Some 1984 through 1986 (Julian Date 016) THM 200C transmissions may experience a 2-1 coastdown clunk condition. This condition occurs as the transmission shifts to first gear just before the vehicle stops.

To service a 1984 through mid 1986 (prior to Julian Date 016) THM 200C transmission (Figure 1) for this condition the following steps should be performed.

1. Check engine idle speed and set to specifications.

2. Check the rear differential back lash and repair if necessary.

3. On a 1984 or 1985 THM 200C transmission built prior to September 25, 1985 (Julian Date 268), remove the spacer plate and drill the 2nd and 3rd clutch exhaust orifice out to 3.57 mm (9/64") (Figure 2). Using a 6.3 mm drill bit, hand chamfer both sides of the hole slightly, to remove burrs and rough edges.

4. On a THM 200C transmission built prior to January 10, 1986, Julian Date 016, replace the rear internal gear and output shaft with the new pressed on assembly, (Figure 3) Part Number 8633910.

5. Upon reassembly of the transmission, reduce the transmission output shaft rear end play to .10 mm - .38 mm (.004 - .015 inches) by using a thicker selective washer, if required. Do not let rear end play get lower than .004 inches. Transmission damage may result.

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.