Balance Shaft Noise

TSB #03-06-01-024A - (09/25/2003) Rattle Noise In Engine

 (Install Timing Tensioner Kit)
1996-2003 Chevrolet Astro, Blazer, Express, S-10, Silverado
1996-2003 GMC Jimmy, Safari, Savana, Sierra, Sonoma 1996-2001 Oldsmobile Bravada with 4.3L V6 Engine (VINs W, X -- RPOs L35, LU3)

This bulletin is being revised to clarify warranty description information.

Please discard Corporate Bulletin Number 03-06-01-024 (Section 06 -- Engine/Propulsion System)

Condition Some customers may comment on a rattle-type noise coming from the engine at approximately 1800 to 2200 RPMs.

 Cause The spark, rattle-type noise may be caused by torsional vibration of the balance shaft.

Correction If detonation noise is present , perform detonation/spark knock diagnostics first.

Install a new tensioner assembly kit using the procedure below.

 Remove the engine front cover.
Refer to SI for engine front cover removal procedure.
Remove the crankshaft sensor reluctor ring and line up the timing marks on the crank gear and cam shaft gear.
Remove the camshaft gear and chain.

For model years 1996-1998, remove the crankshaft sprocket using J 5825-A. Pull the shipping pin and discard.
Remove the nylon timing chain tensioner blade from the timing chain tensioner bracket. Position the bracket on the front of the engine. The upper two attaching holes of the bracket will line up with the center two engine front cover bolt holes. The lower bracket holes will line up with the engine front cover alignment holes. Use a hammer and the J 46165 Pin Driver to install the dowel pins through the two lower holes in the bracket and into the engine block. Make sure that the bracket is held firmly in place before proceeding.

For model years 1996-1998, install a roller-type timing chain set. Install the crankshaft sprocket using the J 5590 Crankshaft Gear Installer.
Install the timing chain around the crankshaft sprocket and position the timing chain to the driver's side of the engine.
Install the nylon timing chain tensioner guide onto the timing chain tensioner bracket pin and position the top of the guide under the tab at the top of the bracket.
Install the camshaft sprocket into the chain and then to the camshaft.
Install the bolts finger-tight. Make sure the timing marks are aligned, then tighten the camshaft sprocket bolt. Tighten

Tighten the bolt to 25 N·m (18 lb ft).

Install the crankshaft reluctor ring.
Install the engine front cover and place a washer under the two center cover bolts that extend through the tensioner bracket. These washers are required to maintain the proper crush on the engine front cover seal. Tighten

Tighten the bolts to 12 N·m (106 lb in).

Parts Information
Part Number; Description; Qty 12458911;
Chain kit; 1 89017257;
Tensioner; 1 10220906;
Oil pan gasket; 1 88893989;
O ring and gasket kit; 1 3754587;
Water pump gasket; 2 89017259;
Cover; 1

Parts are currently available from GMSPO.

Warranty Information For vehicles repaired under warranty, use: Labor Operation; Description; Labor Time J1944;
Tensioner, Timing Chain - Install; 0.2 hr Add;
To Replace Crankshaft Gear; 0.2 hr Add;
To Clean Parts On Vehicle over 48,280 km (30,000 mi); 0.3 hr Add;
with A/C; 0.1 hr Add;
S-10 Blazer, Pick Up, S-15 Jimmy, Sonoma With Manual Transmission; 8.4 hrs Add;
S-10 Blazer, Pick Up, S-15 Jimmy, Sonoma and Bravada with Automatic Transmission; 8.8 hrs Add;
T-10 Blazer, Pick Up, T-15 Jimmy, Sonoma With 4WD and Bravada with AWD; 4.1 hrs Add;
Express, Savanna; 3.9 hrs Add;
Silverado, Sierra with Four Wheel Drive; 4.1 hrs Add;
Astro, Safari With All Wheel Drive; 4.1 hrs Add;
Astro, Safari; 3.7 hrs Add; Silverado, Sierra; 3.7 hrs