Cambiamos el carrete del portacarretes.

It can mean either one.

In Spanish, cambiamos is the same form for:

• present indicative: we change / we are changing
• preterite: we changed

So, without context, the sentence is ambiguous. Native speakers usually understand the time from the situation or from extra words, for example:

• Hoy cambiamos el carrete... = Today we change / are changing the reel...
• Ayer cambiamos el carrete... = Yesterday we changed the reel...

Because Spanish usually drops subject pronouns when the verb already makes the subject clear.

The ending -amos in cambiamos already tells you the subject is we. So nosotros is unnecessary in a normal sentence.

You could say Nosotros cambiamos el carrete del portacarretes, but that usually adds emphasis, contrast, or clarity, such as:

• Nosotros cambiamos el carrete, no ellos.
  = We changed the reel, not them.

Del is the contraction of de + el.

So:

• de el portacarretes → del portacarretes

This contraction is normally mandatory in standard Spanish.

Depending on context, de can mean things like:

• of
• from
• out of
• belonging to

In this sentence, del portacarretes could be understood as something like:

• of the spool holder
• from the spool holder

The best English version depends on the technical context.

Spanish uses definite articles more often than English does.

Here, el carrete means the reel / spool, and del portacarretes means of/from the holder. Spanish often includes the article when talking about a specific object already known in the situation.

So even if English might sometimes sound more natural with fewer articles, Spanish often keeps them:

• Cambiamos el carrete del portacarretes.

That structure is very normal.

Carrete can have several meanings depending on context. Common ones include:

• reel
• spool
• bobbin
• sometimes film roll

So the exact translation depends on what kind of machine, tool, or device you are talking about.

That is very common in Spanish technical vocabulary: one word may match different English words depending on the object involved.

It is a compound noun.

It is built from:

• porta- = from portar or the idea of holding/carrying
• carretes = reels/spools

So portacarretes literally means something like:

• reel-holder
• spool holder

Spanish has many nouns like this, for example:

• paraguas = umbrella
• sacacorchos = corkscrew
• lavavajillas = dishwasher

These compound words are very common and often sound more natural in Spanish than a longer phrase.

Because many Spanish compound nouns keep a fixed form that may look plural even when the whole word is singular.

So you can have:

• el portacarretes = the spool holder
• los portacarretes = the spool holders

The article tells you whether it is singular or plural.

This happens with other words too, such as:

• el paraguas / los paraguas
• el sacacorchos / los sacacorchos

So the -s in portacarretes does not automatically mean the whole noun is plural.

It could suggest either kind of relationship, depending on context.

The preposition de is very flexible in Spanish. It can express:

• possession or association: the reel of the holder
• source or origin: the reel from the holder
• part-whole relationships
• material, type, and other links

In a technical or mechanical context, English will often choose the most natural wording, such as:

• We changed the reel in the spool holder
• We changed the reel from the spool holder
• We changed the spool-holder reel

Spanish often leaves that relationship more general with de.

In normal standard Spanish, no.

When de is followed by el, they contract:

• de + el = del

So the correct form is:

• del portacarretes

The only main exception is when El is part of a proper name, such as some place names or titles. But for an ordinary noun like portacarretes, you must use del.

The given order is the most neutral and natural one:

• Cambiamos el carrete del portacarretes.

You can change word order in Spanish, but that usually changes the emphasis rather than the basic meaning.

For example, moving del portacarretes to the front would sound more marked or literary, not like the default everyday version.

So for a learner, the safest pattern is:

• verb + direct object + modifier

Here:

• Cambiamos = verb
• el carrete = direct object
• del portacarretes = phrase modifying carrete

Because el carrete is the direct object, and in Spanish direct objects normally do not take a preposition unless they refer to specific people or sometimes pets.

Compare:

• Cambiamos el carrete. = no preposition, because it is a thing
• Vemos a María. = a is used because it is a person

So el carrete appears directly after the verb with no extra preposition.

Often, in this kind of practical or mechanical sentence, cambiar is best translated as change or replace, depending on context.

For example:

• Cambiamos el carrete could mean We changed the reel
• In many situations, natural English would say We replaced the reel

Spanish cambiar is broader than one single English choice. So the best translation depends on what is actually happening.