HARSH ENGAGEMENT NEUTRAL TO DRIVE OR REVERSE
TRANSMISSION APPLICATIONS: SUBJECT:
1985 THROUGH 1987 THM 125C (MD9) NEW FORWARD CLUTCH ASSEMBLY AND NEW LO AND REVERSE CLUTCH ASSEMBLY
TRANSMISSION MODELS: VEHICLE APPLICATIONS: All Models A, J, N, P, X CARS
BULLETIN COVERS:
New forward clutch assembly, including: a new housing, new Piston, new selective backing plates, and an additional wave plate for improved neutral to drive shift feel.
New lo and reverse clutch housing and lo and reverse clutch pack assembly, including: a new housing, new piston, two wave plates, and selective backing plates for improved neutral to reverse shift feel.
DATE OF CHANGE: (Figure 1)
The new forward clutch assembly implemented July 3, 1986, Julian Date 184, and the new lo and reverse clutch assembly implemented July 8, 1986, Julian Date 189, for all models of the THM 125/125C.
SERVICE ACTION:
1985 and/or 1986 Model Year:
The neutral to drive package can be used to service a 1985 or 1986 (before Julian Date 184) THM 125C transaxle exhibiting a harsh drive engagement by replacing the forward clutch with the new forward clutch assembly.
The neutral to reverse package can be used to service a 1985 or 1986 (before Julian Date 189) THM 125C transaxle exhibiting a harsh reverse engagement by replacing the lo and reverse clutch assembly with the new lo and reverse housing assembly, and new lo and reverse clutch pack assembly. (The lo and reverse clutch pack assembly contains both wave plates, the steel and compositioned-faced plates, and the correct selective backing plate.)
1986 and/or 1987 Model Year:
When servicing the forward and/or lo and reverse clutch assemblies on a 1986 (after Julian Date 184) or 1987 THM 125C transaxle, it is important to select the correct backing plate. The backing plate selection effects piston travel and shift feel.
To check the forward clutch backing plate selection, apply approximately 10 lbs. of pressure on the backing plate and check the gap between the backing plate and snap ring. If the gap is larger than 1.49 mm use the next thicker backing plate and if smaller than 0.67 mm use the next thinner backing plate. Refer to figure 2 for alternate backing plate selections.
The new lo and reverse clutch pack assembly (wave, steel, compositioned-faced, and selective backing plate) is serviced as an assembly only.
SERVICE PARTS INFORMATION
8664167 Forward Clutch Assembly, Complete 8664152 Lo and Reverse Clutch Housing Assembly 8664151 Lo and Reverse Clutch Pack Assembly
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.
