Engine/Transmission - Droning/Moaning Noise (1985)
Transmission Mount: Customer Interest
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.
