How to Replace the Drive Gear in your Garage Door Opener
Its 6am and you are leaving for work. You press the garage door opener wall button and hear a subtle hum from your electric motor but the door failed to move.If your garage doors springs are in tact chances are you garage door openers main drive gear has failed.You can easily inspect your drive gears by unplugging your garage door opener and removing the metal cover. The main drive gear is made of a white plastic that typically is the weak link in the opener.Many things can cause this gear to fail. Some causes of wear are:
Garage door out of balance (Springs broke or in need of adjustment)
Chain to tight a
Excessive use or high cycle
Factory defect or lack of grease at time of manufacture
Replacing the large white gear is a low cost, quick and easy do it yourself repair as long as you have a few simple hand tools and follow the safety precautions.These gears can be purchased online in a variety of levels of components. The following gears and gear kits work with most all models of LiftMaster, Sears Craftsman and Chamberlain brand garage door openers. When ordering the full gear kits that include the sprockets, please make sure that you know if your garage door opener is a chain or belt drive as there are differnet part numbers. If you just want just the gear (such as the 41A2817-CR) then the main drive gear will be the same.
41A2817-CRGear and grease only. Works with all chain and belt models from 1984 to present LiftMaster, Sears Craftsman and Chamberlain openers using a large white gear that is 2 3/4" x 1/2" wide, with a 1/2" bore.
41A2817this kit includes the gear and grease as described above and in addition includes worm gears, replacement bushings, pins and lubricant and easy to follow installation instructions. 41A2817 Works with all chain and belt drive models from 1984 to present Liftmaster, Sears, Craftsman and Chamberlain openers using a large white gear that is 2 3/4" x 1/2" wide, with a 1/2" bore.
41C4220Athis kit includes all of the components above in the and includes the drive shaft and sprocket also. I recommend this kit if you do not have the 5/32 punch as mentioned in our tools requires section.It is cheaper to buy this kit than it would be to run out and buy the punch needed to remove the roll pins to replace the gear only. The main drive gears comes already installed on the shaft (very convenient) This repair kit is FOR CHAIN DRIVE MODELS ONLY. If you have a belt drive model see part number 41A4885-2 or 41A4885-5 below.
41A4885-2use this kit if you wish to replace the complete drive shaft and belt pulley assembly on belt drive garage door openers used between 1984 and 2001. For newer models from 2002 to present see part number 41A4885-5 below
41A4885-5 use this kit if you wish to replace the complete drive shaft and belt pulley assembly on belt drive garage door openers used between 2002 to present.
In the attempt to educate homeowners on the procedure we have produced this article to guide you through the process step by step.After reading this article you cam make an educated decision on whether or not to attempt this procedure yourself.
Before you get started it is important for you to have a list of the few simple tools needed to accomplish this project:
½ wrench or adjustable wrench or pliers
3/8 Socket or Nut Driver
1/4 Socket or Nut Driver
5/16 Socket or Nut Driver
Flat Standard Screwdriver
5/32 Punch or similar
~WARNING ~ To prevent possible SERIOUS INJURY or even DEATH from electrocution,
ALWAYS Disconnect the power cord from your garage door from the
outlet before proceeding with any inspection or repair.
Make sure your garage door opener is unplugged.This step insures that no one unintentionally attempts to open or close the garage door while you are working on it or you do not accidentally activate the door while servicing it.
Disconnect the door from the outer trolley by manually pulling the red disconnect rope and manually close the garage door.
The Garage door MUST be in the fully closed position
during all repairs and inspection.
Assuring that your garage door is closed will reassure that your door will not fall or make any movement that would cause injury or startle you. We recommend that once the door is closed that you clamp the door down using a vise grip or clamp above one of the rollers to prevent the door from being opened from the outside.See photo example below.
Slacken the chain or belts tension by loosing the tension nut on the garage door opener trolley.Typically this is nut and can be adjusted with a ½ wrench
Remove the sprocket or belt pulley retainer cap. Usually this has a clip on the back if you press in it will release.
I always recommend marking the position of the chain or belt to the sprocket prior to removing.This can easily be done with white out, tape or any other means. This step helps assure that your chain or belt gets reinstalled in the correct position and makes for quick and easy reference if needed later. Remove the chain or belt from the sprocket and then slide the inner trolley to the closed position until it engages the outer trolley.Place loose chain/belt on the end of the rail closest to the sprocket.I typically duct tape the chain to prevent it from falling to the floor and getting all twisted and dirty.
It is now time to remove both end covers and the main housing. The end cover are each attached by three or four ¼ head screws that can be removed with a ¼ nut driver or socket. Be sure to unplug the wire to the circuit board.
Remove the retaining clip and the drive gear for the limits.Also at this time remove the limit switch assembly by squeezing the sides just below the bracket by the drive gears.There is no need to disconnect the wires as it is ok to leave this limit assembly hang by the wires. Do not make any adjustments to the limit assembly screws, this will insure that there is minimal adjustment needed to the limits after you complete your repair and run your garage door opener.
Now its time to remove the RPM sensor this can be easily done by unplugging the wire harness and remove the RPM sensor from the securing tabs.
Disconnect the red, blue and white wires from the motor.It is important that you note where these wires go.The same color wires go to the same terminals on the capacitor red/red and blue/blue.See photo examples below.These photos are a good reference if you happen to forget.
Remove the four 5/16 hex head screws that hold the motor assembly to the frame of the garage door opener. Be sure to put your hand under the motor before removing the last screw to prevent the motor from falling. Slide the motor assembly off the drive shaft and place in a safe place. (Not on top of the ladder for obvious reasons)See photos below.
Step #11 Remove the three hex head screws holding the sprocket assembly to the main chassis using a 5/16 nut driver or socket. Now it is time to decide if you want to replace the main gear only all units 1984 to present chain and belt drive use part number 41A2817-CR or the main gear and worm gear part number 41A2817 or the entire sprocket 41C4220A for all chain drive models 1984 to present. For belt drive models if you wish to change the pulley shaft use part number 41A4885-2 from 1984 to present and if your belt drive unit was made from 2002 to present use part number 41A4885-5 all these parts are very affordable and can be purchased online at www.stardoorparts.com. See photo below to locate these screws.
Skip this step if you are replacing the entire gear and sprocket or pulley assembly 41C4220A, 41A4885-2, 41A4885-5. If you are going to replace the drive gear support the driveshaft on a block of wood and drive the lower roll pin/Tension pin out with a 5/32 punch.See photo example below.
Remove and replace the worm gear. In most cases it is not necessary to replace the worm gear unless it shows signs of wear.If you wish to replace this gear remove the shaft collar with a 1/8 hex wrench. Please be sure to note the location of each of these components as you disassemble so you can re-install in proper order.When you receive you kit part number 41A2817 or 41C4220A you will find there are parts not used in your model this is because these kits are universal and work with many models of Sears, Craftsman, Wayne Dalton, Master Mechanic, Liftmaster, True Value and other brands of garage doors openers.Only replace the parts that are used on your garage door opener.Remove the 3 nuts that hold the motor to the frame and then remove the worm gear.Install the new worm gear making sure the roll pin is properly seated in the new gear. Re-install other components in reverse order.After you complete this assembly I recommend you lube the worm gear so you do not forget.
Begin reassembly in reverse order. Be sure to thoroughly lube the main drive gear and that grease is on each and every tooth.Attach the gear and sprocket or pulley assembly to the main chassis with the three 5/16 head screws. Install the assembled motor frame to the chassis with the four 5/16 head screws and reattach the red, blue and white wires; now install the limit assembly and the limit drive gear making sure they mesh properly.You can now install the RPM sensor and reconnect wires. Install the metal cover and end panels, be sure to plug in the circuit board and reconnect photo eye and push button wires.
Reconnect the power cord to the opener and cycle the opener until the sprocket completes a complete clockwise cycle.The trolley must be in the fully down position before installing the chain. Now you can remove the tape from the rail and reinstall the chain. The chain and sprocket reference mark should be close to lining up.Tighten the chain so that the chain is ½ above the base of the rail at midpoint for T style rails and ¼ for square tube rails. Secure the chain tightening lock nut.
Note when adjusting and testing your garage door motor it is important
to make sure no one is in the path of the moving door.
It is important to know when testing your garage door opener it is possible to over cycle the motor
and have the motor temporarily overheat and stop operating.
To prevent this try and not operate the door opener more than 10 cycles
without giving it 5-10 minutes to cool off
Now run the opener and test to see if the door opens to the correct position and closes to the correct position.If you need to make adjustments use the travel adjustments screws to make fine adjustments.I recommend only making slight adjustments ¼ turn or less at a time.For reference one full turn of the screw equals approx 2 of travel on ½ and ¼ HP models and 3 on ¾ HP models.
Once you have your doors travel adjustment correct it is time to adjust the force.This is the pressure that it takes to assure your door opener will operate safely.The first step in this process is to check the down force.With the door open simply activate the garage door opener and when the door reaches the half way point grasp the door from the bottom and try and stop it.If the door is hard to stop or does not stop decrease the down force adjustment in small increments until it reverse upon reasonable force. If the door does not close and the light begins to blink increase the down force adjustment in small increments until you can check the reversal at half way.Adjusting the force does not guarantee that your operator will reverse on 1-1/2 object at the floor.For more information on adjusting the reversal at the floor see your owners manual or call the manufacture.
Some of the models this article covers are listed below and many models are left out.Please e-mail us if your model was not shown but this article helped you out contact usand let us know so we can add your make and model number to the list to help out more people.