Multipoint Lock Gearbox Guide: How to Identify the Right Replacement

A faulty multipoint door lock can make a uPVC or composite door difficult to lock, even when the handle and cylinder appear normal. Often the problem is the centre gearbox—the mechanism behind the handles that operates the wider locking system.

What is a multipoint lock gearbox?

A multipoint lock typically secures a door at several positions along its edge. Depending on the design, these may include hooks, rollers, bolts or a central deadbolt. The gearbox, sometimes called the centre case or lockcase, contains the mechanism that transfers movement from the door handle and key to the locking strip.

In many systems, the centre gearbox can be replaced without replacing the entire multipoint locking strip—but only when a compatible replacement is available and the rest of the mechanism is serviceable. If you are replacing the cylinder rather than the gearbox, use our euro cylinder measuring guide to check the correct size.

Common signs of gearbox failure

• The handle lifts but the locking points do not move correctly.
• The handle feels loose, stiff or fails to return.
• The key will not turn when the door is closed, or turns only with difficulty.
• The latch or deadbolt sticks or does not retract.
• The door locks with difficulty even after checking its alignment.

Important: These symptoms are not proof of a broken gearbox. Door misalignment, worn hinges, a faulty cylinder, damaged handles or a jammed locking strip can cause similar problems. Avoid forcing the handle or key, as this can make the damage worse.

How to identify the correct replacement gearbox

Multipoint gearboxes are not universal. Two centre cases may look nearly identical yet have different dimensions or internal operation. Before buying, compare the following:

1. Manufacturer and markings: Check the faceplate and centre case for names or codes such as GU, ERA, Yale, Maco, Winkhaus, Fuhr, Lockmaster, Mila, Fullex, KFV or Roto.
2. Backset: Measure from the front edge of the lock faceplate to the centre of the spindle hole. Common dimensions include 35 mm and 45 mm, but other sizes exist.
3. PZ or centres: Measure from the centre of the handle spindle to the centre of the euro-cylinder keyhole. Do not assume all gearboxes use the same centres.
4. Spindle arrangement: Identify whether the case uses a single through spindle, split spindle, dual follower or another arrangement.
5. Latch and deadbolt: Check whether the centre case has a latch only, latch and deadbolt, hookbolt or another configuration.
6. Case dimensions and fixing positions: Compare height, width, depth and the position of mounting screws.
7. Operation: Confirm whether the mechanism is lift-lever, key-wind, automatic locking or another system.

Understanding backset and PZ measurements

The backset is the distance from the faceplate’s front edge to the centre of the spindle. The PZ measurement is the vertical distance between the centre of the spindle and the centre of the euro-cylinder opening. Both must match the intended replacement. For split-spindle and dual-follower gearboxes, additional measurements may be necessary.

Gearbox only or complete multipoint lock?

A gearbox-only replacement may be appropriate when the centre case has failed but the full-length locking strip, connecting rods and locking points are undamaged and compatible. If the strip is bent, corroded or seized, or if the replacement centre case cannot be matched accurately, replacing the complete mechanism may be the better solution.

Can you replace it yourself?

Some replacements are straightforward for experienced tradespeople, but incorrect fitting can leave a door insecure or unable to open. If a door is jammed shut, the lock is under tension, or you are unsure about compatibility, consult a qualified locksmith or door-repair specialist. Do not dismantle a locked door in a way that could trap occupants or compromise emergency exit.

Shop multipoint gearbox replacements at Lockora

At Lockora, we are building a range of replacement multipoint gearboxes and door hardware for common UK door systems. Availability varies, and some catalogue items are listed for identification while stock or exact specifications are being confirmed.

Browse multipoint gearbox products or contact us for help identifying a part. Include the manufacturer marking, backset, PZ measurement, spindle arrangement and clear photos of the existing gearbox if possible.

Questions? Email info@lockora.co.uk.