VIBRATION NOISE AT IDLE INFORMATION

Model and Year 1984 CORVETTE

TO: ALL CHEVROLET DEALERS

This cancels and replaces Chevrolet Dealer Service Bulletin #84-151 dated June, 1984 which should be destroyed. This bulletin is being reissued to cover additional part revisions for this condition.

Some 1984 Corvettes may exhibit the subject noise, which is commonly defined as a "moan". This noise is induced into the subject components by belt excitation when the air conditioning is "on".

This condition can be assisted by the following:

1. Using three (3) new tubular braces and fasteners to replace the single rear generator brace. This will stiffen the generator mounting.

2. Replace the existing power steering bracket with a new stiffer (ribbed) bracket, P/N 14087559.

Vehicles produced after VIN E5137968 have already utilized the new tubular generator braces.

All 1985 vehicles have both the new tubular braces and power steering bracket.

The following components are required for this service procedure:

Quantity P/N Description -------- --- ----------- 1 14057002 Stud 1 3932448 Stud 1 2436163 Washer 3 14057004 Nut 1 14066303 Bolt/Screw 1 14063755 Bolt/Screw 1 14084334 Brace 1 14084335 Brace 1 14084336 Brace 1 14087559 Bracket

To insure proper installation, the following steps are to be performed:

1. Remove the generator rear support brace. Discard the support brace, attaching nut and attaching bolt.

2. Remove and discard #1 and #3 L.H. exhaust manifold to cylinder head attaching bolts (see Figure 1).

3. Install stud, P/N 14057002, in place of discarded #1 bolt and torque to 35 N.m.

4. Install stud, P/N 3932448, and washer, P/N 2436163, in place of discarded #3 bolt and torque to 35 N.m.

NOTICE: Washer is to be installed on stud between stud hex and exhaust manifold.

5. Remove the serpentine belt from the generator pulley.

6. Remove power steering bracket and replace with new bracket, P/N 14087559. This new bracket is a direct replacement for the existing bracket, therefore, should be installed as outlined in the 1984 Corvette Shop Manual, Page 3B9-5.

7. Install three (3) tubular braces on the exhaust manifold studs as shown on Figure 2 and loosely retain with attaching nuts in three (3) places.

8. Install bolt, P/N 14066303, in longer single brace and bolt, P/N 14063755, in two (2) short braces. Loosely install bolts into generator housing (see Figure 2).

9. Mandatory torque sequency (Figures 1 and 2):

Generator lower attaching bolt 50 N.m.

Generator upper attaching bolt 50 N.m.

Long tubular support brace to generator, attaching bolt 35 N.m.

Two (2) short tubular support braces to generator, attaching bolt 50 N.m.

Three (3) tubular support braces to three (3) exhaust manifold studs, 25 N.m three (3) attaching nuts.

NOTICE: The B+ wire on the generator should not contact the support brace(s). If necessary, disconnect the battery and loosen the B+ cable eyelet, on the generator, and rotate the B+ wire to clear the support brace(s). Retorque the eyelet attaching nut and install the battery cable.

10. Reinstall serpentine belt.

Labor Operation Number: T1109

Labor Time : 1.1 hours

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.