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Before you startKeep the door open while checking the lock. Never force the handle, key, latch or deadbolt.

Door lock help · GU Old Style replacement

GU 35 mm gearbox support

Deadbolt moving around? Latch facing the wrong way? Check these simple points before fitting your replacement.

  • 35 mm backset
  • 92 mm PZ
  • Single spindle
A moving deadbolt does not mean it is broken.

On this replacement, the deadbolt can move or sit at an angle before the gearbox is fitted to the locking strip. This movement is normal for the design shown and is not, by itself, a fault.

My deadbolt is looseWhy it moves before fitting Reset after deliveryBring the deadbolt back in Reverse the latchTurn the bevel the other way. Short animation.

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The GU Old Style 35 mm replacement gearbox: the long faceplate with the small bevelled spring latch and the larger square deadbolt projecting from it, and the euro cylinder cut-out near the bottom.
The replacement shown in this guide · GU Old Style, 35 mm backset, 92 mm PZ

TL;DR

The essentials in 30 seconds

  1. Keep the door open. Check everything with the door open and never force the handle, key, latch or deadbolt.
    Door-open test
  2. A loose deadbolt is normal before fitting. On this replacement the locking strip guides the deadbolt once the gearbox is attached. Angled on the bench is not, on its own, a fault.
    Why it moves
  3. Moved in the post? Use the handle. With a correctly fitting handle and spindle, lower the handle gently to retract the deadbolt. No screwdrivers, pliers or hammers.
    Reset it
  4. Latch the wrong way round? Twist it. The small bevelled spring latch turns through a half-turn. The larger deadbolt is not the part to twist.
    Watch the animation
  5. Match the model, not just 35 mm. This guide is for the GU Old Style 35 mm backset, 92 mm PZ, single-spindle replacement only.
    Check the fit
  6. Still won't lock once fitted? Stop. Don't close the door or force the key. Send us photos.
    Get help

01 · Know which part you are moving

The latch and the deadbolt are different parts

Both project from the front edge of the gearbox, but they do different jobs. The instructions are not interchangeable.

  • Spring latchThe smaller tongue with a sloping, bevelled face, near the top. It moves back into the case and returns under spring pressure. This is the part you twist to reverse the handing. Show me how to reverse it
  • DeadboltThe larger, flat rectangular tongue below the latch. On this loose replacement gearbox it can move around until it is guided by the locking strip. Do not twist the deadbolt to reverse the latch. Watch the normal movement
A newer-made replacement for an older lock

“GU Old Style” is the lock family this gearbox replaces. The changed construction does not make this a different “GU New Style” gearbox.

02 · Looks different from the original?

The locking strip guides the deadbolt

Your original gearbox may have held the deadbolt more rigidly. On the replacement shown here, the long metal locking strip guides it once the gearbox is correctly attached.

With the gearbox loose, the deadbolt can move, project out of the case or sit at an angle — including after movement during delivery. An angled deadbolt on the unfitted gearbox is not, on its own, evidence that the gearbox is faulty.

Animation · Why the loose deadbolt moves · 12 seconds. Before fitting, the larger flat deadbolt rocks back and forth while remaining in the gearbox. The smaller spring latch stays still. The deadbolt finishes in a straight position; movement is normal while this replacement is off the locking strip.
Animation · How the locking strip guides the deadbolt · 14 seconds. The deadbolt rocks while the locking strip is separate. It straightens, then the teal strip moves into position around the latch and deadbolt. Once fitted, the strip guides the deadbolt and it stays aligned. This animation explains the movement; it does not show the attachment steps.
The strip is not the frame keep

The locking strip runs along the edge of the door and the gearbox attaches to it. The keep is the receiving fitting on the door frame.

There is no need to exchange this gearbox simply because the unfitted deadbolt moves. Start with the reset below. If the correctly fitted lock still will not work, use the troubleshooting checks rather than assuming the problem is only free movement.

03 · After movement in the post

Bring the deadbolt back in with the handle

These steps are for the intact replacement gearbox shown here, where the deadbolt has moved out before fitting. They are not a repair for a detached or damaged part.

Animation · Reset the deadbolt using the handle · 16 seconds. The handle points left. Lowering it gently retracts both the spring latch and the deadbolt. When the handle is released, it returns to its starting position and the latch springs out again, leaving the deadbolt retracted. Support the gearbox and never force the mechanism.

  1. Support the gearbox

    Hold the case securely with fingers clear of the moving parts. If you are working at the door, keep it open throughout.

  2. Use a correctly fitting handle and spindle

    Use the square handle-spindle opening to operate the gearbox. Do not use the cylinder opening as a lever, and do not force a screwdriver into the mechanism.

  3. Gently lower the handle to retract the deadbolt

    With the handle correctly fitted, move it down gently: this retracts both the latch and the deadbolt on the replacement shown. Keep the deadbolt aligned with its opening as it returns. Raising the handle projects the deadbolt. Do not hammer it, bend it or force it straight with pliers.

  4. Check that the mechanism returns smoothly

    Check that the spring latch moves in and returns when the handle is released. The deadbolt can still have movement while the gearbox is off the strip; resetting does not turn it into the more rigid original design.

Stop if it will not return with gentle operation

A part that has completely fallen out, damaged metal or persistent jamming needs checking. Do not open the gearbox casing or force the mechanism. Send us photographs for advice.

04 · Left-hand or right-hand door

Twist the spring latch to reverse it

The latch on this replacement is reversible. Turn the smaller, bevelled latch — not the larger rectangular deadbolt.

Animation · Reverse the spring latch · 12 seconds. The smaller bevelled spring latch turns through 180° so its sloping face points the other way. The larger deadbolt stays still. The animation shows the change in direction; follow the written steps to check that the latch moves in and springs back out afterwards.

  1. Check which way the bevel needs to face

    Compare it with the original lock or a photograph taken before removal. The sloping face needs to meet the frame keep as the door closes.

  2. Twist the latch through a half-turn

    Hold the case and gently turn the spring latch through 180° so the bevel faces the opposite way, as shown in the animation. You do not need to open the gearbox casing for this reversal.

  3. Let it settle back and check its movement

    Check that the latch moves back into the case and springs out again. If it resists or stays stuck in, stop and ask us to check it.

Only follow this twist-reversal method for the replacement shown

Other GU models and other manufacturers can use different release arrangements. If yours looks different, do not force it.

05 · Make sure it is the right gearbox

Match the model, not just the 35 mm measurement

This guide is for the GU Old Style 35 mm replacement centre-case gearbox, single spindle, supplied by UPVCSTORE under Amazon ASIN B0BT54TFQT.

Backset
35 mm. Measure from the front face of the lock faceplate to the centre line of the handle spindle.
PZ
92 mm. The centre-to-centre distance from the handle spindle to the cylinder/key centre.
Operation
Single spindle. Also compare the case shape and its attachment points to your locking strip.

The supplied drawing is reproduced unchanged. Its backset dimension is labelled “Backset”; the 35 mm value comes from the product specification, not a number added to this drawing.

Supplied gearbox dimension drawing, showing 92 mm PZ and a backset line labelled Backset. Other original dimension labels are retained.
Supplied technical drawing.
Open for a closer look.
35 mm alone is not a compatibility check

Do not assume these instructions apply to GU New Style gearboxes, other backsets, different spindle arrangements or other brands. Professional fitting is advised.

Want to see a gearbox being fitted?Search YouTube for how to install a multipoint door lock gearbox and pick any video that matches your lock.

Search YouTube

Bought from our website rather than Amazon? The same replacement is listed as GU gearbox door lock centre case, Old Style replacement, 35 mm. Compare your gearbox with the listing photographs before ordering another.

06 · Before closing the door

Test the complete lock with the door open

The loose gearbox is not the complete locking mechanism. Final checks need the correct gearbox properly reconnected to its matching locking strip, with the handle and cylinder correctly fitted.

  1. Check the assembled mechanism

    Confirm that the gearbox is correctly attached to the strip and that its connections are properly engaged. If you are unsure how to reconnect it, use an installer rather than guessing.

  2. Check the latch and handle

    With the door open, operate the handle gently. The latch should retract and return, and the mechanism should move without sticking.

  3. Check the full locking and unlocking cycle

    Follow the normal operating sequence for your matching multipoint lock. Confirm that the key operates correctly and all locking points fully retract again before considering closing the door.

Not sure how the gearbox goes back onto the strip?Search YouTube for how to install a multipoint lock onto the strip upvc door and pick any video that matches your lock.

Search YouTube
If it still will not lock or unlock, stop

Do not close the door or force the key. A problem after correct assembly is not explained away by normal free movement on a loose gearbox.

07 · Still unsure?

Find the symptom that matches yours

The deadbolt is loose, crooked or sticking out of the new gearbox.

On this replacement, that can be normal before the gearbox is attached to the locking strip. Watch the animation, then reset it gently using the handle and spindle. This advice does not cover bent metal, a detached part or a correctly fitted mechanism that still jams.

The latch faces the opposite way to my original.

The small bevelled spring latch is reversible on the replacement shown. Twist it through 180° and check that it moves in and springs back out. Do not twist the deadbolt instead.

The small latch moves into the case when I use the handle.

The spring latch is intended to retract. Check that it returns when released. If it stays in, binds or will not return, stop and send us a photograph or a short clip.

Everything moves, but my key still will not lock it after fitting.

Do not assume this is just the normal deadbolt movement. Keep the door open. Have the model match, gearbox-to-strip connection, cylinder and full lock operation checked. Send us clear photographs and tell us whether it works with the door open. Do not force the key.

It operates with the door open but not when I try to close it.

That can point to an alignment or fitting problem, rather than the loose-gearbox movement described above. Do not force the door, handle or key. Keep the door open and have the fit and alignment checked.

A part has fallen out, the metal is damaged, or it will not reset.

Stop fitting it. Normal movement does not mean detached parts, damage or persistent jamming should be ignored. Contact product support with photographs. Do not dismantle the case or try to straighten parts with tools.

Do I need to return it and order the same gearbox again?

Not simply because the deadbolt moves before fitting or the spring latch needs reversing. Another example of the same replacement design can behave in the same way. Use the relevant checks above. You can still use the normal order-help or returns route if the part is damaged, wrong for your door or not working correctly; following this guide is not a condition of asking for help.

08 · Get the right help

Send us the part — not just the symptom

Clear photographs help us distinguish normal movement, a model mismatch and a fitting or mechanical problem.

  1. A complete view of your original gearbox and the replacement, with any markings visible.
  2. A view of the locking strip and how the gearbox is attached.
  3. A close-up or short clip of the latch or deadbolt, plus whether the lock operates with the door open.
  4. Your order reference and where you purchased it.
Send photos on WhatsApp Email sales@upvc-store.com

If the door cannot be secured, arrange help from a qualified installer or locksmith. We reply during staffed hours.

Bought this on Amazon?

For order issues or a return, open your Amazon order and use its help or return options. Amazon purchases do not go through our website’s order-return portal. Open your Amazon orders.

This is a product-use guide, not a requirement to troubleshoot before requesting order help or a return. It does not mean every reported locking problem is normal.