Dubto que puguem desmuntar el canvi de marxes.

Dubto means I doubt.

It is the 1st person singular present of dubtar = to doubt.

So:

• dubto = I doubt
• dubtes = you doubt
• dubta = he/she/it doubts

In this sentence, Dubto que... means I doubt that...

In Catalan, when you say I doubt that..., you normally use:

dubtar + que + subjunctive

So:

• Dubto que puguem... = I doubt that we can...

That que introduces the subordinate clause, just like that in English.

Very often, English drops that:

• I doubt we can do it

But Catalan normally keeps que:

• Dubto que puguem fer-ho

Because dubto que triggers the subjunctive in Catalan.

So after dubto que, you use the subjunctive form of poder:

• podem = we can / we are able to → indicative
• puguem = that we can / may be able to → subjunctive

That is why the sentence is:

• Dubto que puguem desmuntar...

and not:

• Dubto que podem... ❌

This is a very important pattern in Catalan: expressions of doubt, possibility, emotion, desire, etc. often require the subjunctive.

Puguem is the 1st person plural present subjunctive of poder = to be able to / can.

A few present subjunctive forms of poder are:

• jo pugui
• tu puguis
• ell/ella pugui
• nosaltres puguem
• vosaltres pugueu
• ells/elles puguin

So puguem means that we can / that we may be able to.

Desmuntar usually means to take apart, to dismantle, or sometimes to remove by taking apart.

In mechanical contexts, it often means physically disassembling something.

So here it suggests something like:

• taking apart the gear mechanism
• removing it by dismantling it
• disassembling the gear system

It is built from:

• muntar = to assemble / mount
• desmuntar = to disassemble / take apart

Literally, el canvi de marxes is something like:

• the change of gears
• or more naturally, the gear mechanism, gear shift, or gearbox, depending on context

Breakdown:

• el = the
• canvi = change / shifting / gear mechanism
• de marxes = of gears

In real usage, this kind of phrase often refers to the system used to change gears in a vehicle or machine.

Because the idea is gear changing in relation to multiple gears.

• marxa can mean gear
• marxes = gears

So canvi de marxes is literally gear change or gear-shifting system, involving more than one gear.

This is similar to how English often uses a plural idea in expressions like gears or gear changes, even if the full phrase is translated more naturally in the singular.

Catalan often uses the definite article where English may or may not use one.

Here, el canvi de marxes means the gear mechanism / the gearbox / the gear shift as a specific object.

So the sentence is talking about a particular, identifiable thing:

• el canvi de marxes

This is completely normal in Catalan.

Not with exactly the same meaning or tone.

• Dubto que puguem... = I doubt that we can...
• No sé si podem... = I don't know if we can...
• Dubto si... is much less natural here for most learners' purposes

So if you want to express genuine doubt in a standard, idiomatic way, dubto que + subjunctive is the safest choice.

Yes. This is completely standard.

After a conjugated form of poder, the next verb usually stays in the infinitive:

• podem desmuntar
• puguem desmuntar
• poden arreglar
• pugui venir

So in the sentence:

• puguem desmuntar

you have:

• puguem = conjugated verb
• desmuntar = infinitive

This works like English can dismantle.

The structure is:

Dubto + que + puguem desmuntar + el canvi de marxes

Piece by piece:

• Dubto = I doubt
• que = that
• puguem = we can / we may be able to
• desmuntar = dismantle / take apart
• el canvi de marxes = the gear mechanism / gear shift / gearbox

So the grammar pattern is:

main clause + que + subjunctive clause

That is a very common Catalan pattern.

Yes, in standard Catalan, dubtar que normally takes the subjunctive.

So:

• Dubto que vingui
• Dubto que sigui possible
• Dubto que puguem desmuntar el canvi de marxes

This is one of those patterns worth memorizing as a unit:

dubto que + subjunctive

If you learn it that way, sentences like this will feel much more natural.