The LiftMaster K39-34786 clutch disc is a factory replacement friction disc used in select LiftMaster industrial slide gate operator clutch assemblies. It helps transfer drive force through the clutch while allowing controlled slip when the clutch is adjusted correctly. This small part matters because a worn, glazed, cracked, or oil-contaminated clutch disc can make a heavy slide gate slip, hesitate, chatter, or lose pulling power even when the motor is still running.
Product Details
This disc is used inside the mechanical clutch stack, between clutch plates and drive components. In the field, it is commonly replaced when the operator runs but the gate does not move consistently, when the clutch cannot be adjusted to hold proper torque, or when the old disc has been damaged from excessive slipping. It is not a cure for a dragging gate, bad rollers, damaged chain, or incorrect clutch adjustment, so the full drive system should be inspected before replacing only the disc.
Compatible With
This part is commonly associated with the following LiftMaster applications when the operator parts diagram calls for this exact service part:
- LiftMaster SL585U slide gate operators when the parts diagram specifies K39-34786 or 39-34786
- LiftMaster SL585UL slide gate operators using this clutch disc size
- LiftMaster SL585GL legacy slide gate operators where the original clutch disc matches this part
- Select LiftMaster industrial slide gate clutch assemblies that call for the 2-1/2 inch OD x 1-1/2 inch ID disc
- LiftMaster slide gate operators only when the original part number or exploded parts diagram confirms K39-34786
Features and Specifications
| Manufacturer | LiftMaster |
| Product Type | Clutch disc / clutch disk |
| Part Number | K39-34786 |
| Application | Mechanical clutch assembly for select industrial slide gate operators |
| Compatible Operator Type | Select LiftMaster SL585 series slide gate operators |
| Outside Diameter | Approximately 2-1/2 in |
| Inside Diameter | Approximately 1-1/2 in |
| Notes | Verify the original disc size and parts diagram before ordering |
Also Known As / Related Part Numbers
- K39-34786
- 39-34786
- K3934786
- 3934786
- LiftMaster clutch disc
- LiftMaster clutch disk
- SL585 clutch disc
- SL585UL clutch disc
Technician Note
If the gate slips after installing a new clutch disc, check gate travel resistance, chain alignment, rollers, clutch spring, clutch plates, and adjustment. Over-tightening the clutch can defeat the intended slip function and create a safety concern.
Before Ordering Checklist
- Confirm the operator model is in the SL585 family or the parts diagram lists K39-34786
- Compare the old disc outside and inside diameter
- Inspect the clutch plates for glazing, grooving, oil, or uneven wear
- Correct gate drag or chain alignment problems before adjusting the clutch
- Verify monitored safety devices and force/obstruction response after service
Professional Advisory
Commercial gate clutch service should be performed by a qualified gate technician when the gate is heavy, high-cycle, or showing repeated obstruction faults. Do not bypass safety devices or tighten the clutch to overcome a mechanical gate problem.
Product Questions and Answers
What does the K39-34786 clutch disc do?
It provides friction inside the operator clutch assembly so the drive can transfer torque while still allowing controlled slip when properly adjusted.
Which operators commonly use K39-34786?
It is commonly listed for LiftMaster SL585 series slide gate operators, including SL585U, SL585UL, and legacy SL585GL references when confirmed by the parts diagram.
Is K39-34786 the same as 39-34786?
Yes. 39-34786 is a common related part-number format for the LiftMaster K39-34786 clutch disc.
Should clutch discs be replaced in pairs?
On many worn clutch assemblies, replacing related friction surfaces together provides more consistent adjustment, but the exact requirement should follow the operator parts diagram.
Can this fix a gate that is hard to move?
Not by itself. A dragging gate, damaged chain, bad rollers, or tight track must be corrected before clutch adjustment will hold properly.
