GMC P35 Ignition Lock Cylinder Guide: 1975-1978
Having trouble with a stuck key or a no-start situation in your 1975-1978 GMC P35? Your ignition lock cylinder might be the culprit.
- Failure symptoms are almost always mechanical, such as a key that is stuck, loose, or hard to turn.
- New aftermarket parts from brands like Dorman and Standard Ignition are the standard, reliable repair option for these older vehicles.
- Replacement is a DIY-friendly job but requires special tools like a steering wheel puller and lock plate compressor.
- A new lock cylinder will come with a new set of keys; your old keys will not work.
Is Your Ignition Lock Cylinder Failing?
On a workhorse vehicle like the GMC P35, the ignition lock cylinder endures decades of use. The small metal pins and tumblers inside wear down over time. This wear and tear is the most common reason for failure. Because this is a mechanical part, the signs of a problem are usually straightforward and easy to spot. If your key turns fine but the truck has electrical problems like no power to the dashboard or the engine stalls, the issue is more likely the separate ignition switch, not the lock cylinder.
Choosing the Right Aftermarket Part
For a vehicle from the 1970s, new original equipment manufacturer (OEM) parts are generally no longer available. The most practical and common solution is a new aftermarket part. Both Standard Ignition (Standard Motor Products) and Dorman are well-regarded brands that produce reliable replacement ignition lock cylinders for these trucks. They are designed to match the fit and function of the original part. A new lock cylinder will come with a new set of keys.
Cost of Replacing a 1975-1978 GMC P35 Ignition Lock Cylinder
| Part Type | Part Cost | Estimated Labor Cost | Total Estimated Cost |
|---|---|---|---|
| New Aftermarket (Dorman, Standard Ignition) | $25 - $35 | $100 - $200 | $125 - $235 |
| New OEM | Unavailable | $100 - $200 | N/A |
Installation Overview
Replacing the ignition lock cylinder is a manageable job for a DIYer with some mechanical experience. However, it does require special tools: a steering wheel puller and a lock plate compressor. These can often be rented from auto parts stores. The basic process involves disconnecting the battery, removing the steering wheel horn pad, nut, and the wheel itself. Then, you use the compressor tool to remove the lock plate retaining ring. With the lock plate out of the way, you can access a small slot on the housing; inserting a thin tool or screwdriver into this slot depresses a retaining tab, allowing the old cylinder to be pulled straight out.
Pro Tip: The lock cylinder usually needs to be in the 'ON' or 'RUN' position to be removed. If your key is completely stuck and won't turn, you may need to carefully drill out the retaining tab as a last resort to remove the cylinder.
Frequently Asked Questions (FAQ)
How do I know if it's the lock cylinder or the ignition switch?
The lock cylinder is mechanical, while the ignition switch is electrical. If your symptoms are physical—like a key that's hard to turn, gets stuck, or feels loose—the problem is likely the lock cylinder. If the key turns perfectly but the engine doesn't crank, or if accessories randomly lose power, the problem is more likely the ignition switch located further down the steering column.
Are there any recalls for the ignition lock cylinder on a 1975-1978 GMC P35?
No. A search of the National Highway Traffic Safety Administration (NHTSA) database did not find any recalls or technical service bulletins (TSBs) specifically for the ignition lock cylinder on these vehicles.
Will my old keys work with the new lock cylinder?
No. A new ignition lock cylinder will always come with a new, matching set of keys. Your original keys will no longer work in the ignition. Some owners choose to replace the door locks at the same time to keep a single key for the entire vehicle.
What tools do I need for the replacement?
Besides basic hand tools, you will need a steering wheel puller and a steering wheel lock plate compressor tool. These are essential for accessing the lock cylinder within the steering column.
Technical Specifications
This is a mechanical lock cylinder with an actuator rod linkage to a separate ignition switch. It does not contain any electronic components or anti-theft chips.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.