Safari Van M V6-262 4.3L VIN Z TBI (1990)
b.
Front propshaft (L vans)
c.
Rear propshafts (M/L vans)
d.
Tuned damper, rear axle pinion nose These parts can only be obtained by establishing a case with GMC Truck Technical Assistance. To identify
the correct system, it is important that the technician follow the flow chart contained in this bulletin (Figure 1 for M Van and Figure 2 for L Van)
to obtain the necessary vibration frequencies prior to calling the Technical Assistance Engineer. GMC Truck Technical Assistance will then
authorize shipment of the needed part(s) to your dealership.
SERVICE PROCEDURE
1.
Road test the vehicle on a smooth surface (preferably asphalt). Use the Electronic Vibration Analyzer (EVA) (J 38792) to obtain the
frequencies/RPMs at points of disturbance. A passenger should be present during the road test to read and record the information.
2.
Use the recorded frequencies/RPMs from the road test to fill in the information on Figure 3.
3.
Follow the EVA BALANCE PROCEDURES below to reduce the vibration complaint.
EVA BALANCE PROCEDURES
1.
Raise the vehicle on a hoist and support it with safety stands. Support the rear axle at the outer most part of the axle tube. Keep the vehicle
supported at curb height.
2.
For reference, mark the propshaft at 90 degree intervals (four locations) with white paint or chalk. These marks will be used for the strobing
function.
3.
L-vans only: remove the front propshaft.
4.
M/L vans: remove the rear tire/wheel assemblies and brake drums.
5.
Inspect the propshaft and U-joints for undercoating. If undercoating is present, it must be removed.
6.
Measure the runout on the rear propshaft and companion flange. There must be no more than 0.025 in. (0.63 mm) runout on the rear propshaft and
no more than 0.015 in. (0.38 mm) runout on the companion flange.
7.
Inspect the rear propshaft and U-joints for any possible damage.
8.
If the runout IS UNACCEPTABLE AND/OR THERE IS DAMAGE, call GMC Truck Technical Assistance for further instructions.
If the runout IS ACCEPTABLE AND THERE IS NO DAMAGE:
a.
Use EVA to system balance the rear propshaft to the rear axle by attaching the accelerometer to the bottom of the pinion nose with the word "UP"
facing UP.
b.
Clip the inductive pickup of an inductive type timing light to EVA's timing light loop and connect the timing light to a 12 volt source.
c.
System balance the rear propshaft to the rear axle using the instructions contained in PPN's reference manual GMC TT-92-03-2 in section 5
"DRIVELINE VIBRATION ANALYSIS".
CAUTION:
DO NOT USE THE CRUISE CONTROL TO MAINTAIN A STEADY SPEED.
Important
DO NOT depress the brake pedal with the rear brake drums removed.
9.
Road test the vehicle. If the vibration is not noticeable, the vehicle is repaired. If the vibration is still present, contact GMC Truck Technical
Assistance for further instructions.
WARRANTY INFORMATION For vehicles repaired under warranty use:
Labor 0p.
Description
Labor Time
J9000
Road Test
Actual Time up
to 0.9 hrs.(*)
T7338
Rear Propshaft
0.2 hrs.
