B3000 SE Regular Cab 4WD V6-3.0L OHV (1998)
Technical Service Bulletin # M00298
Date: 981022
4X4 Vacuum Hub - No 4X4 Operation/Clunk Noise
Bulletin No.: 002/98
Issued: 10/22/98
Revised:
Category
M (03)
Applicable Model/s
1998-99 B-Series 4WD
Subject
NO/INTERMITTENT 4WD OPERATION OR CLUNK NOISE WITH 4WD LIGHT ON
APPLICABLE MODEL(S)/VINS
All 1998-99 B-Series with 4WD.
DESCRIPTION
This bulletin is to be used with the Workshop Manual to assist with the diagnosis and repair of the Pulse Vacuum Hub (PVH) system for the following
concerns:
^
No or intermittent 4WD operation while 4WD indicator light is "ON".
^
Clunking noise while shifting into 4WD on-the-fly.
Customers complaining of either of these concerns should have their vehicle repaired using the following repair procedure.
Repair Procedure
1.
Verify customer complaint.
Note
^
The PVH system is unlike the past 4WD hub systems. It uses engine vacuum to lock/unlock the front hubs and requires different diagnostic
procedures. Be sure not to interpret a 4WD light "ON" and front drive shaft rotation as a properly operating 4WD system.
^
Many customers have reported 4WD LOW issues when they have NOT properly performed the engagement procedure. This procedure
requires ALL of the following conditions to be met before engagement/disengagement can occur:
^
Zero vehicle speed.
^
Foot on brake.
^
Transmission in Neutral (clutch depressed).
^
Move the 4WD control to the 4WD LOW position.
Review these conditions with customers to determine whether they have followed the proper engagement procedure.
^
Most causes of 4WD no\intermittent engagement and noise may NOT be found in the PVH system.
^
Noisy hublocks are frequently a result of other 4WD issues. In these cases replacing the hublocks may not fix the concern.
2.
First inspect the following areas to ensure that the noise is from the PVH system. Refer to Workshop Manual.
^
Transfer case clutch relay and wiring connections.
^
Transfer case shift motor (related Generic Electronic Module (GEM) codes)
^
Front driveshaft CV joint damage
^
Front axle bolts missing or loose
^
Front axle half shaft CV joint damage
3.
Place the vehicle in 2WD mode and drive for approximately one mile.
4.
Stop the vehicle, turn the wheels to full lock, and exit the vehicle. Try to rotate both front drive shafts by hand. If the shafts rotate (NOT locked),
proceed to STEP 5.
If the shafts will not turn (ARE locked), proceed to STEP A below.
