Astro Van L AWD V6-262 4.3L VIN W CPI (1992)
Drive Chain: All Technical Service Bulletins
Driveline - Noise Which Resembles Bad Axle Bearings
Number: 93-237-4A
Section: 4A
Date: JUNE 1993
Corporate Bulletin No.: 367402
ASE No.: A2
Subject:
DRIVELINE NOISE WHICH RESEMBLES "BAD AXLE BEARINGS"
Model and Year:
1990-93 L-VANS WITH ALL WHEEL DRIVE
CONDITION:
Some owners of 1990-93 L-vans (AWD) may comment about a driveline noise/rumble under light or moderate loads while driving. This condition
resembles abnormal axle bearing noise when driving under light or moderate loads, and usually occurs on acceleration from 47 to 54 mph. The
noise/rumble that this bulletin addresses will go away by letting up on the accelerator pedal.
IMPORTANT:
Before removal of the transfer case, be sure to complete the diagnostic form and paperwork required by Chevrolet Dealer Service Bulletin No.
92-190B-4A to assure proper diagnostics.
IMPORTANT:
The Borg-Warner 4472 Transfer Case Diagnosis and Exchange program (36 months/36,000 miles) is still available and is encouraged for situations
when it is not clear which component may be causing a concern (reference Chevrolet Dealer Service Bulletin No. 93-82-7D).
CAUSE:
The Borg Warner 4472 Transfer Case is designed with a "random variable pitch" chain, which causes a high frequency tonal sound/noise called
"rumble".
CORRECTION:
A new transfer case chain (P/N 15963558) is available which incorporates straight pitch links instead of variable pitch links. The straight pitch chain will
reduce the tonal noise called rumble.
Vehicles built after the following VIN breakpoints have the new style chain in the transfer case installed in production:
VIN
PB152925
SERVICE PROCEDURES:
IMPORTANT:
Ensure front and rear propeller shafts are marked relative to other driveshaft components before disassembly. These components are match balanced
and MUST be reassembled in the same relationship to each other to maintain proper balance. Refer to Section 4A of the appropriate M/L Service
Manual for further information.
