diagnostic screw drive type openers all use a coupler of some sort this is usually a piece of plastic that attaches the motor on the opener unit to the long 7 foot screw inside the opener rail so that the motor can spin the long screw inside of the opener rail. the good thing about the liftmaster brand is if you get on a ladder and look at the very top of your motor unit the coupler is visible to the naked i it is not contained inside of the opener like other brands. when you are trying to diagnose whether youre liftmaster screw drive opener has broken a coupler. the easiest way to tell is you push the button to operate the opener and you can hear the motor spinning but the garage door or the screw are not moving. also on liftmaster models when the coupler breaks its tends to throw pieces of it all over your garage so you may see a couple of pieces laying on the floor or on top of the motor unit itself. liftmaster screw drive openers are built pretty well they do not usually breakdown that often internally the screw coupler is the most common malfunction on this brand of garage door openers. the coupler is made of plastic and is usually easy to find on the internet and are very inexpensive. i will give you instructions on both options but i would strongly advise you grab somebody to help you perform this task. most garage door technicians work alone but that does not mean we would not mind a helping hand it helps make the job go faster and safer.
cost: $10 $15
difficulty: moderate
time to repair: 60 90 minutes
tools needed: 3⁄8, 7/16, 1⁄2, 9/16 wrench or socket. impact drill (not necessary but recommended). ladder, phillips and flat screwdriver.
there are a couple of different ways that you can do this procedure you can either remove the whole opener unit itself and put it on the floor of your garage. if you decide to replace the coupler by removing the whole opener unit with motorhead and rail together you will have to disconnect all the sensor wires in wall button
wires in order to do this. this can be a bit more time consuming because you have to remove all the wires and then reattach all the wires when you are finished making sure they all go in the correct place. the other option is to leave the opener mounted and just separate the motorhead from the rail and slide in the new coupler and then reattach the rail to the motorhead this option will go much faster because replacing a coupler on a screw drive motorhead usually only takes an experienced technician about 20 to 30 minutes to complete. one more important thing you must remember when it comes to liftmaster screw drive openers is the up and down limits that stop the opener on the way up or on the way down in the correct location the reason is the limit assembly inside a liftmaster opener is driven by the motor inside so you must determine what
position that motor is in so that you know whether it is in a up mode or down mode. you do not want to have the limits backwards because when you go to start the motor for the first time after your repair you could damage parts on the opener. here are the instructions for the two different options you can use.

option 1: removing the entire opener with motorhead and rail

 
step one: first thing that you will need to do is unplug the power cord from the electrical socket this will ensure that the opener does not activate accidentally while you are trying to remove it. next you want to disconnect the hockey arm at the point where it connects to the top section of your garage door. now you will want to put your garage door in the closed position. now you will have to locate the control panel where all of your wires connect to the opener and also where you make adjustments to the up and down force and sometimes depending on the age of your opener or what model it is you will either find the control panel in the very back of the opener. behind the light cover if it is a older model you will find the control panel on the right side of the motorhead usually there is a small door that you pull down it kind of looks like a automobiles access door to the fuel tank. if your control panel is on the right side of the motorhead the wires are usually attached with screws if your control panel is behind the back light cover then the wires are attached to connectors that you push on when you insert the wire to lock it in or unlock the wire to remove it. either way you will have color¬coded wire connectors or if they are connected by screws there will be small colored boxes above each screw the colors will be white red and black or a grayish color instead of black. if the opener was installed with the factory wiring that came with it for the sensors and the wall button you can determine the difference by the color coding of the wires all sensor wire is color¬coded black and white you will have one black wire and one white wire and wall controls will have two wires one white and one red you will just need to match up the color coated wire with the color¬coded screws or connectors to make sure the wiring is correct. it may be a good idea to put a small piece of tape around the ends of the wires so when you need to reconnect them you can label them sensor or wall button to make it a little easier. liftmaster screw drive openers usually have two small channels on each side of the top of the opener rail most of the time technicians will run the sensor wires through the small channels when you are removing the wiring be sure not to pinch or break the wiring. once you have disconnected the sensor and wall button wires you might want to wrap the wiring around something near the ceiling to keep the wiring out of your way when you are removing and replacing the opener unit.
 
step two: now that you have removed all the wiring it is time to remove the motorhead and rail. you will want to start the disconnection process at the motorhead where the punched angle attaches to it there should be a couple of bolts. this is where you should grab somebody to help you you will want them to hold the opener up while you disconnect the bolts so the motorhead does not slam to the floor. once the motorhead is disconnected in most cases you can gently lower it to the garage floor but sometimes the torsion springs if you have them can be right underneath the opera rail on top of your garage door sometimes this will not allow the motorhead to reach the floor if this is the case then have your helper keep the motorhead where it was so that you can go to the front of the opener rail and remove the 3 inch keep her pin and keep her ring that holds the pin in place. if you are having trouble removing the 3 inch keeper. you can have your helper slightly move the opener right or left this should help release the pin. once the pin is removed your opener should be totally disconnected and you can lower it to the floor of your garage to perform the repair.
 
step three: now with the opener on the floor of your garage you need to separate the real from the motorhead you will see two bolts going straight through the rail where it connects to the motorhead just remove these bolts and the rail and motorhead should just slide apart. you will be able to see the coupler before you separate the real from the motorhead because on liftmasters it is exposed on other manufacturers it is not exposed. remove any broken pieces that you may have of the old coupler make sure that they are not in the way when you reattach the rail. when you are sliding the new coupler on you should slide it onto the rail part and slide the rail back into the slots that hold it and you can slightly turn the coupler with your fingers to get the teeth on the motorhead part of the coupler to slide in make sure that the rail is slid into the coupler all the way if it is not you will notice that the mounting holes for the bolts will not line up. once the holes are lined up then you know that the rail is in the proper position. no reinsert the bolts tighten them down and start the process of re¬hanging your opener. when you start to rehang your opener you should start with the front of the rail and re¬attach it to the bracket above your garage door insert the 3 inch pan and then the keeper ring or keeper pin to hold the 3 inch pin in place and then lift up the rear motor head back to the punched angle that mounts the motorhead. . when the motorhead is mounted where it was before you started then it is time to start to reattach the sensor wires and the wall control wires. remembering that the wall control wires will be red and white and the sensor wires will be black and white. if you have a older model liftmaster screwdrive then you can run the sensor wiring through the two small channels on the top of the rail. if youre open there is a late model dan usually there are about three or four white plastic clips on the very top of the opener rail you can run your wiring through the small white clips. the new were model openers do not have the two small channels for the wiring they just give you the white clips that clip onto the top of the rail. after all your wiring is reattached now you will need to plug in your power cord and test the opener. you may have to readjust your open and close limits you will find them on either the right or left hand side of the opener motor head and they are white plastic adjustment screws. each adjustment screw will have a up or down arrow above it this let you know which one is for the upper limit and which one is for the down limit also it will have a curved arrow around the whole pointing in the direction to increase that limit whether it be up or down. once you have reset the limits if you need to and the door is in the proper open and closed position then you have successfully completed this repair.

Option 2: repair

this option is what most garage door technicians will use to replace a screw drive coupler. the reason for this is because it is a lot faster to make the repair than removing the whole opener unit.
step one: like any other repairs on a opener the first thing you want to do is unplug the power cord so the opener unit does not accidentally activated while you are making the repair. the next thing that you want to do is to put your garage door in the open position. the reason for this is because when you separate the opener rail from the motorhead you can let the rail rest on top of the garage door if the door is closed you would have to support that rail or it just falls to the ground. it will also be a lot easier if you had a helper. if you look where the rail meets the motorhead you will see two bolts that go straight through the rail these bolts will need to be removed in order to slide the motorhead away from the rail. you will also need to loosen the two mounting bolts that mount the motor head to the angle hangs that hang down from the ceiling to support the motorhead you do not want to remove these bolts you just want to loosen them up a little bit so you can have some movement on the motorhead.
 
step two: now you will need to gently slide the motorhead back only about 2 to 3 inches it does not take much and remove any old broken parts of the old coupler making sure no pieces are left behind. now he will insert your new coupler on to the teeth that are connected to the screw rail then you will gently slide the motorhead back into place and you might need to turn the coupler with your fingers slightly left or right to get the teeth to line up. you will know if it is correct if you can see the two boats you removed from the rail are lined up with the holes you put them through if they do not line up it is not all the way on. if you are unable to slide the motorhead back a couple of inches for whatever reason then you will have to disconnect the motorhead from the mounting angle so you can freely slide the motorhead back¬and¬forth to insert the coupler. once the rail is all the way in and the holes lineup to mount your boats then go ahead and reattach the two bolts that hold the rail in place. now you will need to tighten up all the bolts that you loose and or removed to rehang the opener. once you have everything tightened up go ahead and plug in your power cord and activate the opener to see if it is working properly you may have to adjust the up and down limits on the opener because when a couple or breaks off sometimes it changes the up¬and¬down limits. you may have to readjust your open and close limits you will find them on either the right or left hand side of the opener motor head and they are white plastic adjustment screws. each adjustment screw will have a up or down arrow above it this let you know which one is for the upper limit and which one is for the down limit also it will have a curved arrow around the whole pointing in the direction to increase that limit whether it be up or down. once you have reset the limits if you need to and the door is in the proper open and closed position then you have successfully completed this repair.