Everyone loves a key that works. It's when the original key gets to be 40+ years old it really starts to suck trying to unlock the car or start it because everything is wore slap out.
To preface this, I'm not going to go through a grunch of GM part numbers. Why? They're like fasteners. GM superseded and interchanged part numbers faster than Taylor Swift goes through boyfriends. So if you want to know what's what with your particular application, you either need to do some due diligence and do some research, or ask questions because you can get LOST in a sea of part numbers trying to find the "correct" lock for your car.
I'm not talking about going to the box store and buying the chinesium pot metal that will last 2 years before the springs pop out of it. I'm talking about the REAL locks. GM (aka Briggs and Stratton [later Strattec]). B&S was the predominant supplier of locks and keys to GM for about 6,000 years. Save for the 40s when B&S had a big strike and car companies crapped bricks. They got a deal with B&S to manufacture their locks at the Rochester carb plant. Pretty ingenious.
For the MOST part, G-bodies use PRETTY much the same types of locks throughout the lineup and from brand to brand. Such as, some door locks from a pickup will fit your G-body. Chevy interchanges with Olds, etc. Some locks won't. Wagons are a unique breed, but here again, they share a lot of lock part numbers across the brands. So a Poncho wagon lock could very well fit your Malibu wagon.
There are basically 3 major part systems to a GM door/trunk lock. There's the lock cylinder, which is the part the key slides into. The cylinder rotates with the key in the case, aka sleeve. That's the outside part of the lock. This is the one that the cap and unit shutter which is designed with a mini key door of sorts that you push the key through to put it in the lock. The shutter keeps dirt and grime out of the lock. That's the intent, anyway. The shutter has two small springs on it to ensure it puts tension on the cylinder to keep it in place inside the case and keeps the shutter tight against the escutcheon again, to keep dirt out of the lock.
The locks are typically held in place with a U-type spring clip, and a gasket is slipped over the case and the back of the cap area squishes the gasket against the door as the clip is slid in from the rear. The small gasket keeps water out of the door. A pawl with a clip to hold it to the back of the lock is installed and hooks in to the lock rod mechanism in your doors.
Here's the absolute bat-sh*t crazy thing about the cylinders. Depending on when it was made, depends on the key slot that it uses. Go ahead, pull out your GM key for your G-body. It has a code letter stamped on one side of it. It's the key slot code that should match up with the lock key slot. Early versions, I believe MAYBE 1986 and prior, used a shutter that has a tab on it. My 85 has the tabbed lock shutters. By 1987, though, for sure, that tab was gone. The tab was only there to ensure you didn't try and put the key in upside down.
Early shutter version with tab (shown upside down)
Late version
Stranger yet, is that you have three different types of lock assemblies. You have the coded ones with keys and tumblers already installed. Basically a full lock ready to install. They come with a set of keys, and have keys to match the key slots in the lock. These are also known as restricted key slots because no other key code letter will fit the lock. There's also uncoded locks that have no tumblers installed, and no keys. The locks are basically bare shells. Strattec still sells kits that you can "build" your own lock.
There is also what they call an urestricted lock. Also known as a universal. The key slot is basically cut where it will accept ANY key code you wish, as long as it's a GM key for the lock. Some aftermarket ignition locks are universal. For example, you can have an A key fit and function in a universal lock, but you can also slide in a C key as well. If the C key is cut the same as the A key, it also will turn the lock. Note, not all lock assemblies are universal.
The latest uncoded lock number for the G-bodies does happen to be universal. So if you have a B or D key, your key will physically enter the lock. 12398554 is one that comes to mind.
The kit has almost everything you need. Even comes with black shutter and cap for those without "chrome". You will need to get tumblers and springs and the spring retainer (. But that's it. Then you can take your original key and use the tumblers to match it to your key. Or, if you are trying to match sets, you can use any key code you wish and get a key cut and then match the tumblers to get a full set.
Now, you're saying..."But what about the glovebox?" Well, crap. The glovebox lock is a stupid snap in deal with a round rotating head and your secondary (oval) key is what operates this. So the oval key does doors, trunk, and glovebox. The ignition key does...well, just the ignition.
The glovebox uses only 4 tumblers. And they're not the same type of tumbler as in the door or trunk locks.
Ideally, you only want ONE key for ignition and ONE key for the doors/trunk/glovebox. If you don't care about having a bunch of keys, then you don't have to do anything but buy lock sets.
Door lock and trunk tumblers
And a glovebox lock tumblers
Here's a set from Jegs that comes coded with keys. All you would need to do now is recode your door locks and trunk lock to match (if you have universal key slot or B keys) and you're golden. It's probably easier to do the other locks because the glovebox lock is such a PITA to remove. Or I'm just too lazy. Haha.
So how do these locks work?
Look at the key tumblers above. Each has a wedge notch on the right that varies in height by about 0.025". They're held in with springs. Without the key in it, there is a spring loaded side bar that wants to move toward the center of the cylinder. But the tumblers keep the bar extended which fits in a groove in the casing. So when the key is out, the side bar keeps the lock cylinder from turning. When the right key with the correct code matching each tumblers wedge height is inserted, the tumbler slots all line up to allow the side bar to be pushed by its springs inward and releases the cylinder. Now it can be rotated.
Ignition locks are USUALLY coded and come with keys. This is a good thing. Early snap in styles have a little gate near the end of the cylinder inside the column that keeps the ignition lock from coming out. Later versions had a notch in the bottom of them that utilized a retaining screw that went into the column and blocked the lock from coming out of the column. Either is NOT easy to take apart. This is one time I'd just buy the lock and key set and roll with it. It's the only key you need anyway for the ignition. Although it is a bear to find a GM A key ignition switch.
Early lock
Later lock style. Note the notch.
To preface this, I'm not going to go through a grunch of GM part numbers. Why? They're like fasteners. GM superseded and interchanged part numbers faster than Taylor Swift goes through boyfriends. So if you want to know what's what with your particular application, you either need to do some due diligence and do some research, or ask questions because you can get LOST in a sea of part numbers trying to find the "correct" lock for your car.
I'm not talking about going to the box store and buying the chinesium pot metal that will last 2 years before the springs pop out of it. I'm talking about the REAL locks. GM (aka Briggs and Stratton [later Strattec]). B&S was the predominant supplier of locks and keys to GM for about 6,000 years. Save for the 40s when B&S had a big strike and car companies crapped bricks. They got a deal with B&S to manufacture their locks at the Rochester carb plant. Pretty ingenious.
For the MOST part, G-bodies use PRETTY much the same types of locks throughout the lineup and from brand to brand. Such as, some door locks from a pickup will fit your G-body. Chevy interchanges with Olds, etc. Some locks won't. Wagons are a unique breed, but here again, they share a lot of lock part numbers across the brands. So a Poncho wagon lock could very well fit your Malibu wagon.
There are basically 3 major part systems to a GM door/trunk lock. There's the lock cylinder, which is the part the key slides into. The cylinder rotates with the key in the case, aka sleeve. That's the outside part of the lock. This is the one that the cap and unit shutter which is designed with a mini key door of sorts that you push the key through to put it in the lock. The shutter keeps dirt and grime out of the lock. That's the intent, anyway. The shutter has two small springs on it to ensure it puts tension on the cylinder to keep it in place inside the case and keeps the shutter tight against the escutcheon again, to keep dirt out of the lock.
The locks are typically held in place with a U-type spring clip, and a gasket is slipped over the case and the back of the cap area squishes the gasket against the door as the clip is slid in from the rear. The small gasket keeps water out of the door. A pawl with a clip to hold it to the back of the lock is installed and hooks in to the lock rod mechanism in your doors.
Here's the absolute bat-sh*t crazy thing about the cylinders. Depending on when it was made, depends on the key slot that it uses. Go ahead, pull out your GM key for your G-body. It has a code letter stamped on one side of it. It's the key slot code that should match up with the lock key slot. Early versions, I believe MAYBE 1986 and prior, used a shutter that has a tab on it. My 85 has the tabbed lock shutters. By 1987, though, for sure, that tab was gone. The tab was only there to ensure you didn't try and put the key in upside down.
Early shutter version with tab (shown upside down)
Late version
Stranger yet, is that you have three different types of lock assemblies. You have the coded ones with keys and tumblers already installed. Basically a full lock ready to install. They come with a set of keys, and have keys to match the key slots in the lock. These are also known as restricted key slots because no other key code letter will fit the lock. There's also uncoded locks that have no tumblers installed, and no keys. The locks are basically bare shells. Strattec still sells kits that you can "build" your own lock.
There is also what they call an urestricted lock. Also known as a universal. The key slot is basically cut where it will accept ANY key code you wish, as long as it's a GM key for the lock. Some aftermarket ignition locks are universal. For example, you can have an A key fit and function in a universal lock, but you can also slide in a C key as well. If the C key is cut the same as the A key, it also will turn the lock. Note, not all lock assemblies are universal.
The latest uncoded lock number for the G-bodies does happen to be universal. So if you have a B or D key, your key will physically enter the lock. 12398554 is one that comes to mind.
The kit has almost everything you need. Even comes with black shutter and cap for those without "chrome". You will need to get tumblers and springs and the spring retainer (. But that's it. Then you can take your original key and use the tumblers to match it to your key. Or, if you are trying to match sets, you can use any key code you wish and get a key cut and then match the tumblers to get a full set.
Now, you're saying..."But what about the glovebox?" Well, crap. The glovebox lock is a stupid snap in deal with a round rotating head and your secondary (oval) key is what operates this. So the oval key does doors, trunk, and glovebox. The ignition key does...well, just the ignition.
The glovebox uses only 4 tumblers. And they're not the same type of tumbler as in the door or trunk locks.
Ideally, you only want ONE key for ignition and ONE key for the doors/trunk/glovebox. If you don't care about having a bunch of keys, then you don't have to do anything but buy lock sets.
Door lock and trunk tumblers
And a glovebox lock tumblers
Here's a set from Jegs that comes coded with keys. All you would need to do now is recode your door locks and trunk lock to match (if you have universal key slot or B keys) and you're golden. It's probably easier to do the other locks because the glovebox lock is such a PITA to remove. Or I'm just too lazy. Haha.
So how do these locks work?
Look at the key tumblers above. Each has a wedge notch on the right that varies in height by about 0.025". They're held in with springs. Without the key in it, there is a spring loaded side bar that wants to move toward the center of the cylinder. But the tumblers keep the bar extended which fits in a groove in the casing. So when the key is out, the side bar keeps the lock cylinder from turning. When the right key with the correct code matching each tumblers wedge height is inserted, the tumbler slots all line up to allow the side bar to be pushed by its springs inward and releases the cylinder. Now it can be rotated.
Ignition locks are USUALLY coded and come with keys. This is a good thing. Early snap in styles have a little gate near the end of the cylinder inside the column that keeps the ignition lock from coming out. Later versions had a notch in the bottom of them that utilized a retaining screw that went into the column and blocked the lock from coming out of the column. Either is NOT easy to take apart. This is one time I'd just buy the lock and key set and roll with it. It's the only key you need anyway for the ignition. Although it is a bear to find a GM A key ignition switch.
Early lock
Later lock style. Note the notch.
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