A/T - 440-T4 Modulator Valve Buzz Noise

Number: 87-203

Section: 7A

Date: AUG., 1987
Subject: MODULATOR VALVE BUZZ NOISE


Model and Year: 1987 CELEBRITY WITH THM 440-T4
TRANSAXLE

FIGURE 1 - THM 440-T4 TRANSAXLE IDENTIFICATION INFORMATION:

TO: ALL CHEVROLET DEALERS


Modulator valve buzz noise can be caused by a missing orificed cup plug in the modulator circuit of the channel plate for transaxles built prior to February 1, 1987, (Julian date 032, Figure 1).

FIGURE 2:

Service Action: (Figure 2)

Remove the transaxle from the vehicle. Remove the channel plate (404) from the transaxle. Install the orificed cup plug (437) from the service package listed in "Service Parts Information". The cup plug is properly installed at 0.0 - 0.5 mm (.020") below the channel plate machined surface and must be staked securely.
Service Parts Information:

service Package Number 8646987 includes the following parts:

- Orificed Cup Plug
- Lower Channel Plate Gasket
- Upper Channel Plate Gasket
- Modulator Port Gasket
- Instruction Sheet

Service Manual Reference:

Refer to the THM 440-T4 Automatic Transaxle Unit Repair section in the appropriate model year service manual for repair procedures.