How to Identify Your Window Gearbox Brand and Model

How to Identify Your Window Gearbox Brand and Model

If you need to repair or replace a window gearbox, identifying the correct brand and model is essential to get the right part first time. A window gearbox is the internal mechanism that converts handle rotation into movement of the espagnolette or locking rods; different manufacturers use different fixings, spindle sizes and cam arrangements. This post explains practical methods for identifying gearbox type, what measurements and photographs to take, and how to match parts whether you are a trade professional or a DIY homeowner.

Why correctly identifying the gearbox matters

Using the wrong gearbox can mean poor locking, security failures or a handle that does not sit flush. Trade professionals need accurate information to order spares quickly; homeowners benefit from saving time and avoiding returns. Matching brand and model ensures compatibility with existing locking arms, keeps and keeps clearances, and preserves weather performance.

Tools and preparation

Before you start, gather a small toolkit and take suitable safety precautions: wear gloves and eye protection, prop the sash if you need to remove it, and work with a helper for heavy or large windows.

• Small screwdrivers and Torx set
• Digital callipers or a vernier for accurate measurements
• Tape measure and a steel rule
• Camera or smartphone for clear photos
• Marker or masking tape for labelling

How to access the gearbox

Most gearboxes are behind the handle rose or inside the sash edge. For casement windows: remove the handle first, then the trim or screw caps to reveal the gearbox faceplate. For tilt and turn windows the gearbox may be inside the frame so you will need to remove the interior trim or part of the beading. Keep screws and small parts labelled as you remove them.

If you are unsure how to remove the handle without damage, photograph the handle and its fixing before loosening. If the window is still under care by a landlord or managing agent, obtain permission before dismantling.

Visual identification: what to look for

Careful visual inspection will often reveal the manufacturer or part number stamped on metal, moulded into plastic or printed onto a sticker. Typical places to check are:

• Faceplate and edge of the gearbox
• Plastic casing around the gearbox
• Handles and spindles for maker’s marks
• End of the gearbox where locking arms attach

Look for stamped codes, logos or alphanumeric part numbers. Many manufacturers imprint a logo: Roto, GU, Maco, Winkhaus and Siegenia are common names in UK casement windows. If there is a recognizable logo, use that as your first lead; if only numbers are present, those may be internal part codes and will require further comparison.

Photograph and document

Take clear photos from several angles: the faceplate, the gearbox edge, the location of the spindle, any cams or rollers, and any stickers. Include a ruler or tape measure in one photo to give scale. Make notes about how the gearbox operates: which way the handle moves to open, whether cams move inwards or outwards, and how many locking points are engaged.

Key measurements to record

Accurate measurements make matching straightforward. Use digital callipers where possible and record these dimensions:

• Backset: distance from the front face of the gearbox faceplate to the centre of the spindle
• Spindle length and thickness: measure the exposed square or round spindle; common square sizes you will encounter include 7mm and 8mm but always measure to confirm
• Overall gearbox length and height: helps match plastic housings and screw positions
• Distance between fixing screw centres on the faceplate
• Height and shape of cams: identify roller, mushroom or hooked cam types

Recognising common brands and model clues

While many gearboxes look similar, there are distinguishing features:

• Roto: often stamped ROTO or shows a distinct logo on metal parts; cam designs and quick-fit clips are common on their casement gearboxes
• GU (Gretsch-Unitas): metal faceplates with specific screw layouts and part numbers beginning GU or similar; the cam shapes and locking rod attachments are often distinctive
• Maco: typically use plastic housings with moulded numbers and may have a recognisable part code format; look for angled cams
• Winkhaus: usually well stamped and sometimes include positional markings for left/right-handed windows
• Siegenia: common on certain OEM windows; look for unique cam profiles and small metal tags on the mechanism

If you cannot find a logo, cross-reference photos and measurements with supplier catalogues or exploded diagrams. Many manufacturers publish technical drawings online; a match by measurement and cam profile will usually be sufficient.

Trade tips for faster identification

For trade professionals: keep a reference folder of photos and common part codes; use your account with suppliers who offer cross-referencing services; when on site, use a labelled kitbox to remove and store old gearboxes to avoid confusion. Contact the window manufacturer if known; they can often supply exact parts using frame or production codes.

DIY guidance and replacement options

Homeowners can often replace a gearbox themselves if they are comfortable with basic mechanical tasks. Order the replacement only after you have measured and photographed the old unit. If the gearbox is part of a welded or integrated espagnolette rod system it may be better to consult a professional. When fitting a new gearbox, check alignment, apply a small amount of suitable grease to sliding parts and test operation repeatedly before refitting trims.

When to call a specialist

If you encounter fractured metal, corroded locking rods, or inability to remove the sash safely, call a competent professional. Also contact a specialist if the window is an unusual heritage or bespoke unit where parts may be obsolete and require adaptation.

Additional resources

For more on how espagnolette systems work and common lock types see our pillar article: espagnolette window locks. Supplier catalogues and manufacturer technical sheets are also useful for cross-referencing part numbers and dimensions.

Conclusion: measure, photograph and compare before ordering. Start by documenting the gearbox with clear photos and the measurements listed above; check for logos or codes and consult manufacturer catalogues or your supplier’s cross-reference service. If in doubt, bring the old unit or photos to your trade counter or contact a recommended installer. Correct identification saves time and ensures the new part provides secure, smooth operation.

Recommended Products

Based on this article, you may find these products helpful:

• ERAB Espagnolette Window Lock Universal Lock Replacement
• Avocet Slimline Offset Window Espag
• In-Line Window Mechanism
• Offset Window Mechanism
• Multipoint Gearbox GU Old Style