LiftMaster K07-8003 Lower Crank for BG770 Barrier Operators
The LiftMaster K07-8003 is a lower crank used in the linkage system of the BG770 barrier gate operator. This crank is part of the mechanical arm movement system that converts the operator drive motion into the lifting and lowering action of the barrier arm. When the lower crank is bent, worn, loose on the shaft, or damaged from impact, the arm may move unevenly, bind, or fail to align correctly at the open or closed position. Barrier gate crank parts are not universal. The crank position, offset, set screw arrangement, and mating link hardware must match the BG770 parts diagram.
Compatible With
- LiftMaster BG770 barrier gate operator. Also searched as part of BG770 / BG790 barrier operator crank-linkage families, but K07-8003 is strongest for BG770 lower crank applications.
Compatibility should be verified by the operator model number, original part number, and replacement-parts diagram. LiftMaster barrier and commercial gate operator parts often look similar across model families but may use different shafts, collars, hubs, link geometry, or mounting hardware.
Features & Specifications
| Manufacturer | LiftMaster / Chamberlain Group |
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| Product Type | Lower crank replacement |
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| Part Number | K07-8003 |
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| Application | Barrier gate arm linkage assembly |
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| Compatible Operator Type | LiftMaster BG770 barrier gate operator |
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| Material / Finish | Steel mechanical crank |
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| Related Numbers | 07-8003, G078003 |
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| Notes | Match crank position and parts diagram before ordering |
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Also Known As / Related Part Numbers
- K07-8003
- 07-8003
- G078003
- LiftMaster lower crank
- BG770 lower crank
Technician Note
Before replacing this part, check the surrounding mechanical assembly for looseness, worn pivot points, damaged shafts, missing set screws, bent linkage, or signs of a gate or arm impact. Replacing one worn part without correcting the cause can lead to repeat failure.
Before Ordering Checklist
- Match the manufacturer part number and any older Q/G/07-series number to the original part or parts diagram.
- Confirm the operator model, series, and mechanical assembly location before ordering.
- Inspect adjacent shafts, cranks, bearings, fasteners, and linkage hardware for damage or wear.
- Do not order by appearance only; similar LiftMaster mechanical parts may not interchange.
Important Ordering Warnings
- Inspect the arm hub, crank link, upper crank, and shaft for damage if the barrier arm was hit.
- Do not swap upper and lower crank parts; crank geometry and linkage position matter.
Professional Advisory
Mechanical gate and barrier operator repairs should be performed with the operator secured and power disconnected by a qualified gate technician. If the operator has impact damage, binding, unsafe movement, or high-voltage wiring exposure, have the full system inspected before returning it to service.
Product Q&A
What operator does K07-8003 fit?
K07-8003 is most strongly associated with the LiftMaster BG770 barrier gate operator lower crank assembly.
What does the lower crank do?
It is part of the linkage that helps raise and lower the barrier arm by transferring motion from the drive assembly.
Is G078003 the same as K07-8003?
G078003 and 07-8003 are commonly listed as related or alternate numbers for the K07-8003 lower crank.
Can I use this on a BG790?
Do not assume BG790 fitment for this lower crank. BG790 uses related barrier linkage parts, but the parts diagram should confirm the exact crank number.
What else should be inspected with this part?
Check the arm hub, crank link, shaft, fasteners, and barrier arm hardware for wear, impact damage, or looseness.
