I wanted a tailgate that locks and unlocks automatically. I have installed hundreds of door locks over the years but tailgates are bit different. Typically aftermarket door locks clip onto an interior rod or cable attached to the latch and sometimes they work well and other times they don't. The last car I did was an EVO VII which I actually went to the junkyard and got oem actuators for it.
I pulled the 8 t-25 torx screw off the tailgate access panel to see what is there to work with
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The late model GM tailgates don't have an interior lock rod to attach to. What you do have is an arm off the back of the key cylinder that moves a fork. The fork slides a pin to block the handle from engaging the latch opening rods.
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Typically a key cylinder will move around 45 degrees from vertical center to lock/unlock and returns to center. The Colorado tailgate is unlocked at vertical center and moves 90 degrees to lock stays there. This creates a problem where if the lock fork was to be moved by an actuator, it can't, since it is already up against lock cylinder arm. The lock cylinder arm only moves freely when the key is inserted.
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To remedy these problems, you need to create a new lock arm. First the throw needs moved 45 degrees so the center of the arm throw is with the key in the vertical position. You can start by copying the original arm with key-way rotated 45 degrees. Once this is complete, you will notice that even with the lock arm centered and the contact point as narrow as it can be, the lock arm still can't fully move in either direction. To overcome this, the key-way hole needs to be widened. This enables the arm to be able to rotate back and forth while the lock cylinder is stationary. The key will have to rotate a little before it engages the arm.
I traced the original arm onto a posterboard template and transferred that to aluminum. I cut the aluminum with tin snips and ground down the shape on a belt sander then bent with pliers. The key-way was made with a hole punch and file.
paper template
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lock arm photo
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new lock arm
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Now with the lock cylinder arm reworked, you need a way to the move lock lever. This can be accomplished in different ways, I chose to use a Silverado oem tailgate actuator(I got it from amazon $35 shipped). It rotates instead of moving in a linear motion of aftermarket actuators. The Silverado has a vertical post on the lock arm for the actuator to engage. The bottom of the post has a spring locator. This can be emulated on the Colorado. The spring is located in the same place on the Colorado arm, drill and tap the spring locator hole to 10-32. Use a vented cup point set screw to make post(available at MCmasterCarr) and place the spring into the bottom of the set screw vent hole. My pictures actually show a 8-32 shcs and relocated hole for the spring which I used for testing. The relocated spring performed poorly.
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With the lock arm prepped, the actuator needs mounting. The actuator's bracket does not line up with anything on the Colorado. There are two holes on either side of the opening that can be used for mounting. A new bracket can be made for the actuator. A nice bracket would take me 2-3 hours to design, cut, bend up, and get some gussets welded on. I chose to simply make an adapter plate to go between the tailgate and the original actuator bracket. This only took 10 minutes to make and test a posterboard template. Then another 15 minutes to scan, clean up, and cut on a plasma table. There was 1/8" plate already on the table so that is what the adapter is made of. I countersunk the actuator holes and used ss flat head m6 to attach actuator. I used ss m6 button heads and serrated flange nuts to bolt up the assembly to the tailgate.
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Whew, now on to the easy part, Wiring up the actuator. The actuator uses the same connector as the bed lights and a few other things. The connector, terminals, and seals are available through Mouser. I removed the camera, untaped the sleeving and ran actuator wires through the sleeving. I removed the 6 pin Molex MX150 connector and replaced with an 8 pin. Much cleaner with one connector. Unfortunately the hole in the bed for the connector to pass through is a smidgen too small for the 8 pin. I simply
ground off one of keying locators and the connectors squeezes through.
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continued next post
I pulled the 8 t-25 torx screw off the tailgate access panel to see what is there to work with
The late model GM tailgates don't have an interior lock rod to attach to. What you do have is an arm off the back of the key cylinder that moves a fork. The fork slides a pin to block the handle from engaging the latch opening rods.
Typically a key cylinder will move around 45 degrees from vertical center to lock/unlock and returns to center. The Colorado tailgate is unlocked at vertical center and moves 90 degrees to lock stays there. This creates a problem where if the lock fork was to be moved by an actuator, it can't, since it is already up against lock cylinder arm. The lock cylinder arm only moves freely when the key is inserted.
To remedy these problems, you need to create a new lock arm. First the throw needs moved 45 degrees so the center of the arm throw is with the key in the vertical position. You can start by copying the original arm with key-way rotated 45 degrees. Once this is complete, you will notice that even with the lock arm centered and the contact point as narrow as it can be, the lock arm still can't fully move in either direction. To overcome this, the key-way hole needs to be widened. This enables the arm to be able to rotate back and forth while the lock cylinder is stationary. The key will have to rotate a little before it engages the arm.
I traced the original arm onto a posterboard template and transferred that to aluminum. I cut the aluminum with tin snips and ground down the shape on a belt sander then bent with pliers. The key-way was made with a hole punch and file.
paper template
lock arm photo
new lock arm
Now with the lock cylinder arm reworked, you need a way to the move lock lever. This can be accomplished in different ways, I chose to use a Silverado oem tailgate actuator(I got it from amazon $35 shipped). It rotates instead of moving in a linear motion of aftermarket actuators. The Silverado has a vertical post on the lock arm for the actuator to engage. The bottom of the post has a spring locator. This can be emulated on the Colorado. The spring is located in the same place on the Colorado arm, drill and tap the spring locator hole to 10-32. Use a vented cup point set screw to make post(available at MCmasterCarr) and place the spring into the bottom of the set screw vent hole. My pictures actually show a 8-32 shcs and relocated hole for the spring which I used for testing. The relocated spring performed poorly.
With the lock arm prepped, the actuator needs mounting. The actuator's bracket does not line up with anything on the Colorado. There are two holes on either side of the opening that can be used for mounting. A new bracket can be made for the actuator. A nice bracket would take me 2-3 hours to design, cut, bend up, and get some gussets welded on. I chose to simply make an adapter plate to go between the tailgate and the original actuator bracket. This only took 10 minutes to make and test a posterboard template. Then another 15 minutes to scan, clean up, and cut on a plasma table. There was 1/8" plate already on the table so that is what the adapter is made of. I countersunk the actuator holes and used ss flat head m6 to attach actuator. I used ss m6 button heads and serrated flange nuts to bolt up the assembly to the tailgate.
Whew, now on to the easy part, Wiring up the actuator. The actuator uses the same connector as the bed lights and a few other things. The connector, terminals, and seals are available through Mouser. I removed the camera, untaped the sleeving and ran actuator wires through the sleeving. I removed the 6 pin Molex MX150 connector and replaced with an 8 pin. Much cleaner with one connector. Unfortunately the hole in the bed for the connector to pass through is a smidgen too small for the 8 pin. I simply
ground off one of keying locators and the connectors squeezes through.
continued next post
