The GM Genuine Parts 09129242 is an OE-spec crankshaft balancer bolt for select Chevrolet, Buick, GMC, and Cadillac engines. It is listed in the article as an M18 x 1.5 bolt with a 50 mm length. This small part matters because it helps secure the harmonic balancer or crankshaft pulley with the right clamping force.

This review explains what the bolt is, who should buy it, when to skip it, and what installation precautions matter most. Always confirm fitment and torque values with your vehicle service manual before installation.

Key Takeaways

• GM Genuine Parts 09129242 is described as an OE-grade crankshaft or harmonic balancer bolt.
• The article lists the bolt as M18 x 1.5 with a 50 mm length.
• It is intended for select Chevrolet, Buick, GMC, and Cadillac engines where this exact part fits.
• Correct preload, thread condition, and vehicle-specific torque are important for safe installation.
• Do not reuse the bolt if it is stretched, corroded, damaged, or shows head wear.

Key Specifications

What Is This Product?

The GM Genuine Parts 09129242 is a replacement engine fastener. It is used to secure the harmonic balancer or crankshaft pulley to the crankshaft on compatible GM engines.

This is not a decorative part or a universal hardware-store bolt. The thread size, length, head design, material strength, and clamping force all matter. A wrong bolt may create pulley movement, poor preload, vibration issues, or thread damage.

The source article describes this part as an OE-spec M18 x 1.5, 50 mm bolt. That makes it a direct-fit style replacement only when your vehicle calls for this exact part or matching specification.

Who It Is For

• Buy this if your GM service information lists part number 09129242 for your engine.
• Choose it if you want an OE-style crankshaft balancer bolt instead of a generic fastener.
• It suits engine repair jobs where the old balancer bolt is stretched, worn, corroded, or damaged.
• It is useful during harmonic balancer, crankshaft pulley, timing cover, or front engine service.

Who Should Skip It

• Skip it if your engine uses a different thread size, length, or OE part number.
• Do not buy it based only on vehicle brand. Chevrolet, Buick, GMC, and Cadillac vehicles use many different engines.
• Skip it if you need a complete balancer installation kit with washers, tools, or other hardware.
• Do not use it as a universal replacement for any M18 bolt unless your manual confirms the match.

Key Features

OE-Style Fit

The main reason to buy GM Genuine Parts 09129242 is fit accuracy. A crankshaft balancer bolt must match the crankshaft thread and balancer design. The source article identifies this bolt as an OE-spec part for select GM engines.

M18 x 1.5 Thread Size

The article lists the thread size as M18 x 1.5. This detail matters because thread pitch controls how the bolt engages with the crankshaft. A wrong pitch can damage the crankshaft threads.

50 mm Length

The article lists the bolt length as 50 mm. Length affects engagement depth and clamping force. A bolt that is too short may not hold correctly. A bolt that is too long may bottom out or damage parts.

Preload and Clamping Force

The bolt helps create the clamping force that holds the harmonic balancer in place. Proper preload helps reduce movement between the balancer and crankshaft. That matters because pulley movement can lead to vibration, noise, and part damage.

Clear Replacement Criteria

Replace the bolt if it shows stretching, corrosion, damaged threads, rounded head edges, or fatigue marks. Do not rely on appearance alone if your service manual says the bolt is torque-to-yield or single-use.

Real-World Use

This bolt is most useful during front engine repair work. Common jobs may include harmonic balancer replacement, crankshaft pulley service, timing cover work, or related engine maintenance.

Before installation, clean the crankshaft threads and inspect the old bolt. Compare the new bolt with the removed one. Check thread pitch, length, head shape, and washer design if your application uses one.

Use a calibrated torque wrench. Do not guess by hand feel. The original article mentions torque ranges, but torque can vary by engine, model year, and service procedure. Use the exact torque and angle steps from your service manual.

Installation Tips and Maintenance

Start with clean mating surfaces. Dirt, rust, oil, or old thread locker can change clamping force. Clean the bolt hole carefully and avoid forcing the bolt if it does not start by hand.

Use thread locker only if your service manual calls for it. Some applications require dry threads. Others require lubricant, sealant, or a specific thread locking compound. The wrong condition can change the final clamping force.

Torque the bolt in stages if the service procedure requires it. Some crankshaft balancer bolts need a torque-plus-angle method. This is why the vehicle manual is more important than a general torque number.

After installation, listen for pulley noise, belt tracking issues, or unusual vibration. If any problem appears, stop using the vehicle and recheck the work.

Pros and Cons

Is It Worth the Price?

GM Genuine Parts 09129242 is worth considering if it matches your exact engine application. A crankshaft balancer bolt is not a part where you should choose only by low cost. Fit, thread quality, correct length, and proper clamping force matter more.

For a simple repair, an OE-style replacement can reduce guesswork. It may also help avoid the risk of using a generic bolt with the wrong thread pitch, shoulder shape, or strength rating.

The value is strongest when your manual, parts catalog, or mechanic confirms that 09129242 is the correct bolt for your vehicle.

Alternatives

These alternatives are mentioned only for context. Do not use them unless they match your exact vehicle and service manual.

• ACDelco GM Original Equipment crankshaft balancer bolt: A common OE-style option for some GM applications.
• Dorman crankshaft pulley bolt: An aftermarket option that may fit some vehicles, depending on engine and part number.
• ARP harmonic balancer bolt: A performance-focused option for some engine builds, when the correct ARP part is specified.

Frequently Asked Questions

Is GM Genuine Parts 09129242 a universal bolt?

No. Treat it as a specific replacement part. Use it only when your vehicle information confirms the part number, thread size, and length.

What is the thread size?

The source article lists the thread size as M18 x 1.5.

What is the length?

The source article lists the length as 50 mm.

Can I reuse the old crankshaft balancer bolt?

Do not reuse it if it is stretched, corroded, damaged, rounded, or worn. Also replace it if your service manual says the bolt is single-use.

What torque should I use?

Use the torque specification from your exact vehicle service manual. Torque can vary by engine, model year, and repair procedure.

Does it fit all Chevrolet, Buick, GMC, and Cadillac engines?

No. The article mentions those brands, but fitment depends on the exact engine and model year. Always confirm before buying.

Final Verdict

The GM Genuine Parts 09129242 is a practical OE-style crankshaft balancer bolt when your vehicle calls for this exact part. The article identifies it as an M18 x 1.5, 50 mm bolt for select GM engines.

Buy it for fit confidence, correct replacement work, and safer engine service. Skip it if your application needs a different part number or torque procedure. For this kind of fastener, correct fit matters more than guesswork.