What are the first symptoms of uPVC door gearbox failure?

A handle needing more force month on month, then crunching at the top of the lift. Later stages are a floppy handle, a key that turns without locking, and finally a door jammed shut.

My handle lifts but the key won't turn — is it the gearbox or the cylinder?

Test with the door open: a sweet mechanism points to the cylinder; a stiff lift or blocked final turn points to the gearbox.

Can a uPVC gearbox be repaired rather than replaced?

Occasionally — jams caused by debris or a failed spring can be freed. Stripped gears cannot be un-stripped, and a quality replacement outlasts a patched original.

How long does a uPVC gearbox replacement take?

Typically 45–60 minutes when the matching pattern is carried in the van, including door alignment so the new gearbox isn't killed by the same fault.

What does a uPVC gearbox replacement cost on average?

On average £85 labour plus a £20–£180 gearbox plus VAT, with alignment included. Rare or obsolete mechanisms can cost more and are quoted before work starts.

Will opening a door jammed by a failed gearbox damage the door?

No — most are opened by manipulating the mechanism. If drilling the failed gearbox is unavoidable it is agreed first, and because that part is replaced anyway the finished door shows no trace.

Door Repair

uPVC Door Gearbox Replacement: Symptoms, Diagnosis & What’s Involved

Max the Locksmith · July 2026

The short answer: the gearbox is the small central unit in your uPVC door’s locking strip that turns handle-lifting into hooks-throwing — and it’s the part that fails when a misaligned door gets forced for months. Learn its warning sounds below and you’ll catch it as a planned visit instead of a locked-out emergency. Only the gearbox gets swapped — not the whole mechanism, never the door — and Max carries the common Nottingham patterns (Ferco, GU, Maco, Fuhr) in the van. Flat £85 labour + parts (+ VAT), gearboxes averaging £20–£180 — price guide.

First: prove it’s the gearbox (the open-door test)

Open the door, lift the handle in mid-air, turn the key. Everything smooth with the door open = the gearbox is healthy; the door has dropped so its hooks fight the keeps — you need alignment, not parts, and that’s the cheaper visit. Stiff, crunchy, floppy or stuck even with the door open = the gearbox itself. Same test, same logic, as the uPVC door won’t lock guide — it’s the single most useful thing to tell Max on the phone.

The five stages of gearbox death (catch it early)

Gearboxes almost never die unannounced. In order: (1) the handle needs more force each month — that’s not “the door settling”, that’s friction transferring into the gears; (2) it crunches at the top of the lift; (3) the key turns without throwing the deadbolt, or won’t turn at the final click; (4) the handle flops with no spring return — the follower spring has gone, and the rest is close behind; (5) it jams solid — usually down, usually with the door shut, which is how a modest planned repair becomes a same-evening emergency opening. Stage 1–2 callers get the cheapest visits; stage 5 callers still get fixed, just less conveniently.

Two related symptoms that confuse people: a handle that’s stiff only in winter or after rain usually means the door is swelling and dragging (seasonal swelling guide) — alignment again; and a key that spins uselessly is normally the cylinder, not the gearbox — different part, cheaper fix.

Know your part: gearbox vs cylinder vs full strip

Three parts get blamed for each other, and naming the right one is how you avoid the classic overcharge. The cylinder is the barrel the key enters (£25–£120 — and the moment to go anti-snap). The gearbox is the central case behind the handles. The full multipoint strip is the door-length rail with hooks and rollers (see what a multipoint mechanism is) — it only needs replacing when hooks or rails are physically damaged. Paying strip money for a gearbox symptom is the overcharge to watch for; whichever part failed on yours, you’ll be shown it and told why. The full identification walk-through lives in uPVC & composite lock types.

Gearboxes also differ by function — split-spindle doors (handle won’t open from outside without the key — common on newer composites) and lever-lever doors use different cases, and the brand is stamped on the faceplate along the door edge. Photograph that stamp and WhatsApp it over: it’s the fastest route to the right part on the first visit.

What the swap involves (and why alignment is included)

Handles off, cylinder out, faceplate screws out, old case split from the strip, matching pattern spliced in, everything re-timed and tested — 45–60 minutes when the pattern’s in the van. Then the part that separates a repair from a repeat: the door gets aligned and the keeps adjusted, because nine gearboxes in ten were killed by a dropped door, and a new gearbox in a still-dropped door is next year’s job booked in advance. Cheap pattern copies exist with thinner metal and smaller springs — they’re why some “repaired” doors fail again in a year; Max fits genuine or proven equivalents only.

If the exact gearbox isn’t on the van

The common patterns cover most Nottingham doors, but uPVC systems from certain years hide oddities. When yours is one: the door is opened (if jammed), made lockable and secure the same day — there are honest temporary options, from re-timing the mechanism to a secured-keep arrangement — and the correct case goes in when it lands, usually next morning. A door is never left unlockable overnight, and you’ll never be pushed toward a full strip just because it’s the part on the shelf.

What it costs (on average)

On average a gearbox swap lands at £85 labour + £20–£180 parts + VAT, alignment included. Full strips, when genuinely needed, average £40–£250 — though some rare or premium mechanisms (obsolete systems, high-security patterns) can run £250–£500+, and if yours is one you’ll know the figure before any work starts. Deadlocked-shut openings run the same flat pricing day and evening, overnight (10pm–6am) from £95 + VAT. Price guide.

Quick answers

What are the first symptoms of uPVC gearbox failure?

A handle that needs more force month on month, then crunching at the top of the lift. Those two stages are the cheap-visit window — the later stages are floppy handles, keys that turn without locking, and a door jammed shut.

My handle lifts but the key won’t turn — gearbox or cylinder?

Test with the door open: if the mechanism runs sweetly, suspect the cylinder; if the lift is stiff or the key still won’t make its final turn, the gearbox. The stiff/sticking/spinning guide covers the cylinder side.

Can a uPVC gearbox be repaired instead of replaced?

Sometimes a jam is debris or a failed spring and freeing it is honest work — but stripped gears are stripped. A quality replacement outlasts a patched original; when repair beats replacement applies to gearboxes too.

How long does gearbox replacement take?

45–60 minutes when the pattern’s in the van — most swaps are one visit across Nottingham, West Bridgford, Arnold, Hucknall, Derby and Mansfield.

Is it the same part on composite doors?

Same family, thicker slab — composite-specific quirks (seasonal bowing, split-spindle setups) are covered in the composite lock guide.

The door is jammed shut with a failed gearbox — will opening it wreck the door?

No — most open by manipulating the mechanism. Where drilling the failed gearbox is genuinely the only way, it’s agreed first, and since that part is being replaced anyway the finished door shows no trace. See how jammed doors get opened.

Sorted? What most readers check next

Handle getting heavier every week? That’s the cheap-visit window — call 07552 421433, £85 + parts (+ VAT), no call-out fee, same-day.

Need a locksmith in Nottingham?

Max diagnoses the fault, fixes it on the spot where possible, and agrees the price first — £85 + parts, no call-out fee, same price across Nottingham, Derby, Mansfield & Loughborough.

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