Engine/Transmission -Droning/Moaning Noise

No.
09-02-86

P-672

Date
February 24, 1986

Index
ENGINE

Subject
"Moan or Drone" at 1600-2100 Engine RPM

Models
1984-1986 Rear Wheel Drive Domestic Passenger Cars
1981-1986 "D" Series Trucks With Automatic Transmission

SYMPTOM/CONDITION

Passenger Car & Truck

These vehicles may exhibit a moaning or droning noise which occurs at approximately 1800 engine rpm (for V8 engines), or 2100 rpm (for 6- cylinder engines), in any gear.

This noise is sometimes misdiagnosed as an "exhaust system drone", it is not always caused by the exhaust system.

Addition of a damper weight to the rear of the transmission extension can help reduce this noise. Only the A904/A999 transmission extension has provision for mounting this weight; it cannot be used with the A727 transmission.

Truck Only

A new rear engine mount insulator, which also reduces the moaning noise. It can be used on all trucks, including those with the A727 transmission. Trucks with the A904/A999 transmission can use the weight, and the rear engine mount.

PARTS REQUIRED

For all subject trucks:

1 Engine Rear Support Insulator Assembly PN 4412962
(A904, 999 and 727 transmission)
2 Screw/Washer Assembly PN 6029770

For trucks or passenger cars with A904/A999 transmission order:

1 Damper Weight Assembly PN 4412542
1 Plate PN 3681614
2 Washers PN 6032046
2 Screws - PN 6032047

REPAIR PROCEDURE

It will be necessary to install a damper weight and/or rear transmission support to correct this condition.

Truck

1. To replace the engine rear support insulator assembly:

a. With the vehicle on a hoist, position a transmission jack and raise the rear of the transmission and engine slightly.

b. Remove the rear mount through-bolt.

c. Remove the insulator assembly and spacers from the bottom of the transmission extension housing.

d. Install the new insulator assembly on the transmission extension, with the spacers between the screws and the insulator bracket. Use new screws and torque them to 50 foot pounds.

e. Reinstall the rear mount through-bolt and torque to 50 foot pounds.

f. Remove the transmission jack.

2. To install the damper weight assembly:

a. Position the damper weight assembly and plate on the mounting pad at the extreme rear end of the transmission extension. The plate must be in between the weight and the transmission extension.





b. Install the screws and washers as shown in Figure 1, and torque the screws to 150 inch pounds.

Passenger Car

1. Remove existing damper weight from transmission extension.

2. Install new damper weight, making sure that spacers and washers are installed as shown in Figure 1. Torque screws to 150 inch pounds.

POLICY: Reimbursable within the provisions of the warranty

TIME ALLOWANCE:

Labor Operation No. 21-95-40-91 0.2 Hrs.

FAILURE CODE: OX - Wrong Part