LiftMaster Model J Drive Components - DDM Garage Doors Blog

Posted November 6th, 2020 at 6:46 pm by Dan Musick

One of the more common LiftMaster Operators is the jackshaft operator. The operator transfers energy as torque power from the motor to the counterbalance shaft in order to open a sectional overhead door. When the counterbalance shaft turns, it opens or closes the door. In this video, we trace the torque as it moves from the LiftMaster operator’s motor to the door.

In this video, you can see how the mechanical drive components of a LiftMaster Model J operator work.

The torque power begins with the motor drive shaft. Secured to this is the small pulley that moves the v-belt. This belt then transfers torque to the clutch pulley, which we explain in this video. To allow for slippage, only pressure plates secure the clutch pulley to the clutch assembly. The shaft goes through the operator frame to the other side where washers and a ring clip hold it in place.

Inside the operator frame is a series of sprockets and chains to reduce the operator speed and increase the torque. This assembly transfers torque from the lower clutch shaft to the upper driveshaft. On the right side of the operator, a chain connects the driveshaft to the limit shaft. While the driveshaft turns, limit shaft tells the operator how far the door has opened or closed.

The driveshaft goes through the operator frame to the other side, where a sprocket is secured to the shaft. As the sprocket turns, the drive chain turns the torsion shaft sprocket which is secured to the counterbalance shaft. This in turn opens and closes the door when the motor is running.

LiftMaster Model J Operator

If you need assistance with installing a jackshaft operator, please watch our YouTube video titled, “How to Install LiftMaster Jackshaft Operators.”

This entry was filed under News. You can follow any responses to this entry through the RSS 2.0 feed.

Comments are closed.

Unmatched Support. The Right Part. DIY with Confidence!


Huge inventory of parts and torsion springs for same or next day shipping! Here you will find all you need in the most common sizes of 1 3/4," 2," 2 1/4," and 2 5/8" inside diameter springs. Larger 3 3/4" and 6" inside diameter commercial and industrial springs may require a day or two to ship. You'll also find TorqueMaster Springs, Extension Springs, Self-Storage door springs, steel rolling door springs and springs for one piece single panel doors.

COVID update. Because we care! When picking up parts please wear a mask or keep a distance of six feet.

Please note. Shipping times and costs have changed. Normal transit times are currently not guaranteed, even on next day and second day shipments. Shipping prices on items over eight feet have more than tripled.