A/T - 2-1 Coastdown Clunk
Number 86-7-42 Date 11/86Subject: 2-1 COASTDOWN CLUNK
1984-86 PARISIENNE, BONNEVILLE, AND GRAND PRIX MODELS EQUIPPED WITH THM 200C (MV9) TRANSMISSION
Figure 1 - THM 200C Transmission Nameplate:
Date of Production Change: (Figure 1)
January 10, 1986, Julian Date 016: Rear internal gear pressed on output shaft.
September 25, 1985, Julian Date 268: 2nd and 3rd clutch exhaust orifice changed.
Figure 2 - Typical THM 200C Governor Assembly:
Figure 3 - Typical THM 200C Spacer Plate:
Service Action: (Figures 2 and 3)
To service a 1984 through mid 1986 (prior to Julian Date 016) THM 200C transmission equipped vehicle:
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 "BH" model transmission only, remove the primary spring from the governor assembly (Figure 2).
Figure 3 - Typical THM 200C Spacer Plate:
4. 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 3). Using a 6.3 mm drill bit, hand chamfer both sides of the hole, slightly, to remove burrs and rough edges.
5. 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. Refer to Service Notes in this bulletin.
6. 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.
Figure 4 - Pressed On Rear Internal Gear:
Service Parts Information: (Figure 4)
8633910 - Rear internal gear, output shaft assembly
Service Manual Reference:
Refer to the appropriate model year Service Manual Section.
Service Notes:
All 1984 and 1985 THM 200C models OI, OR, and OU already have the pressed on rear internal gear and do not require replacement.
This bulletin supersedes bulletin 85-7-10 dated February 1985, which now should be destroyed.