Locking systems offer a certain amount of mystery because few of us understand how they work. We look to the expertise of a locksmith to get what we need from keyed locks, but you really don't need one. All Mustang lock cylinders, regardless of location, are known as "Pin Tumbler" or "Radial" locks. This concept dates back thousands of years in various forms. To be able to turn the lock cylinder, all tumblers must fit against key teeth and be lined up perfectly at the cylinder. Tumbler or key pin length must equal key tooth depth in order for the lock cylinder to be turned. Tumbler/key pin overall length is determined by driver pin length. Driver pins are positioned against springs and tumbler/key pins.Few of us are going to go to the trouble of re-keying and tumbling our Mustang lock assemblies, which is another article entirely. We're going to show you how to replace locks and lock cylinders with complete kits from National Parts Depot. Garrett Marks of Mustangs Etc. was kind enough to show us how lock replacement is performed, walking us through each.
All Mustang door lock assemblies from '65-'78 are similar in design. There's a latch mechanism and striker at the B-pillar. There are four linear action rods inside the door. One rod connects the exterior push button and latch. Another one ties the latch and exterior key lock. There's the interior lock button rod, which is tied to the latch, and finally there's the interior door handle actuating rod, which is connected to the latch. The only rod we're concerned with here is the exterior key lock rod, which is disconnected via a quick-disconnect clip at the key lock.The only real difference in latch assemblies is how they function. The '65-'66 latch assembly locks only with the exterior key or, with the door closed, via the push-button lock. From '67-'70, you can depress the interior lock button, then hold the exterior handle button and shut the door for locking. You may also lock with a key. For the '71-'78 models it is the same approach as the '67-'70, except you lift the exterior handle for the close and lock function.
When you install new lock cylinders, give each lock a quick shot of white grease through the keyhole, which will eliminate lock freeze ups. Lubrication is always the key to smooth and predictable function.There are two basic kinds of classic Mustang trunk lock approaches. In '65-'66, the trunk lock is located in the decklid and is an involved lock assembly with a large retaining nut and steel support cylinder. From '67-up, the trunk lock cylinder is more like the passenger doors with a retaining clip and a torsion shaft to the latch.01. Replacement locks and keys are available in kit form from National Parts Depot. Door, ignition, and glovebox lock cylinders should always be keyed together. Trunk locks are always keyed differently. Replacement is easy and can be done in a matter of hours.02. Ignition lock cylinder removal for ’65-’66 is easy. Insert the key and turn it left to the accessory detent. Insert the tip of an open paper clip into the release hole, turn the key further left and the cylinder should pop right out.
If you don’t have a key, you can drill out the lock cylinder or have a locksmith re-key. When you drill, be very careful not to drill into the ignition switch itself. Always disconnect the battery prior to doing any ignition switch work.03. This is the ignition lock cylinder with paper clip inserted. To install the new lock cylinder, reverse the process. Insert with the key at 9 o’clock, turn clockwise, and seat the cylinder. Remove the key and check the ignition switch for proper operation through its detents and that it springs back from the “start” position.04. This is a ’67-’68 ignition switch. Lock cylinder removal and installation works the same way as ’65-’66 using a paper clip inserted as shown.05. The ’69 ignition switch works the same way as well. Turn to the accessory detent at 11 o’clock; insert the paper clip in the release hole. Press and turn the ignition key to the left to 9 o’clock. The lock cylinder should pop out. Installation is exactly the reverse, inserted at 9 o’clock, press into place, and turn clockwise.06.
This is how a typical ’65-’78 Mustang exterior door lock and latch assembly looks.07. This is a typical ’65-’78 exterior door lock cylinder and lever. It is suggested you use the original lock retaining clip and the lock rod quick-disconnect. These nylon quick disconnects are quiet and smooth, but tend to pop out if you are not careful. You can use safety wire to secure them, which eliminates the risk.08. This is what you can expect to see inside the door. Two rods, the exterior button, and key lock, are visible here. The exterior door handle has obviously been replaced as witnessed by new parts and the nylon quick disconnect. The original key lock has the factory metal quick disconnect clip.09. Here, we have disconnected the exterior key lock quick disconnect, which is done with a common flat blade screwdriver. A small pocket screwdriver works best in the door and with the small clip’s release tab.10. The exterior lock cylinder is removed by first removing this spring steel clip retainer.11.
Out comes the lock cylinder. The new lock cylinder installs the same way. We suggest you reuse the old lock cylinder retaining clip and reconnect the rod. Lubricate the door latch with spray-on white lithium grease.12. The trunk latch on the ’65-’66 is secured with two body bolts with integral flat washers. A ½-inch socket removes both of them. Remove the latch and set it aside.13. This coarse thread nut secures the lock assembly and support tube. Out comes the lock from the trunklid.14. This is the trunk lock and support tube with gasket.15. To remove the ’65-’66 trunk lock cylinder, turn the key clockwise as if to open the trunk, depress this pin with a small screwdriver or punch, and remove the lock cylinder. Installation works the same way.16. Insert the lock cylinder at the 2 o’clock position, seat the cylinder and observe the pin, which should pop into position. Center and remove the key. Reinstall the lock assembly into the trunklid and secure with the coarse thread nut and then reinstall the trunk latch itself.17.