Volan i menjač rade dobro.

Because the subject is compound: volan i menjač = the steering wheel and the gearbox/gearshift.

In Serbian, when two singular nouns are joined by i (and), the verb normally goes in the plural.

• volan radi = the steering wheel works
• menjač radi = the gearbox works
• volan i menjač rade = the steering wheel and the gearbox work

So rade is the 3rd person plural form of raditi (to work / to function).

They are in the nominative singular, because they are the subjects of the sentence.

• volan = steering wheel
• menjač = gearbox / transmission / gearshift

Even though each noun is singular by itself, together they make a plural idea, which is why the verb is plural: rade.

Here dobro is an adverb, meaning well.

So:

• rade dobro = work well

It does not agree with the nouns, because adverbs do not change for gender, number, or case.

Compare:

• dobar volan = a good steering wheel
• dobar menjač = a good gearbox
• volan i menjač rade dobro = the steering wheel and gearbox work well

So in this sentence, dobro does not mean good as an adjective; it means well as an adverb.

Yes. Serbian word order is fairly flexible.

You can say:

• Volan i menjač rade dobro.
• Volan i menjač dobro rade.

Both are natural and mean essentially the same thing.

Very roughly:

• rade dobro may sound a bit more neutral
• dobro rade may put slightly more focus on how they work

In everyday speech, both are fine.

Here raditi means to work, to function, or to operate properly.

So rade dobro means that these parts are functioning well.

This verb is very common in Serbian for machines, devices, car parts, and systems:

• Motor radi. = The engine is working.
• Telefon ne radi. = The phone isn’t working.
• Kočnice rade dobro. = The brakes work well.

So this is a very useful pattern to learn.

Usually menjač refers to the gearbox / transmission. In some contexts, people may also use it more loosely when talking about the gear-changing mechanism.

So depending on context, English might translate it differently, but gearbox or transmission is often the safest choice.

If you already know the meaning from context, the important grammar point is that menjač is a masculine singular noun here.

Because Serbian does not have articles like a/an/the.

So:

• volan can mean a steering wheel or the steering wheel
• menjač can mean a gearbox or the gearbox

The exact meaning depends on context.

That is completely normal in Serbian, and learners coming from English often notice this right away.

A few useful pronunciation points:

• nj is pronounced like the ny sound in canyon
• č is like ch in church

So menjač is approximately men-yach.

Also:

• volan is pronounced roughly VO-lan
• rade is roughly RA-de
• dobro is roughly DO-bro

These are only rough English approximations, but they help get you started.

In Serbian Cyrillic, it is:

Волан и мењач раде добро.

Letter by letter:

• Volan → Волан
• i → и
• menjač → мењач
• rade → раде
• dobro → добро

Serbian uses both Latin and Cyrillic, and this sentence is standard in either script.

The infinitive is raditi (to work / to do, depending on context).

Present tense:

• ja radim = I work
• ti radiš = you work
• on/ona/ono radi = he/she/it works
• mi radimo = we work
• vi radite = you work
• oni/one/ona rade = they work

In your sentence, rade matches volan i menjač, which together behave like they.

Grammatically, yes, but the meaning would then depend on context.

• Rade dobro. = They work well.

Serbian often omits pronouns when the verb already shows who is doing the action. But if you want to name the things explicitly, you keep the nouns:

• Volan i menjač rade dobro.

So the full sentence is clearer if you are talking about those specific car parts.

It most naturally sounds like a sentence about car parts or some kind of machine.

• volan strongly suggests a vehicle steering wheel
• menjač strongly suggests a gearbox / transmission

So a learner would usually understand this as a practical statement about a car or mechanical system functioning properly.

Yes, but it means something slightly different.

• Volan i menjač rade dobro. = The steering wheel and gearbox work well.
• Volan i menjač su dobri. = The steering wheel and gearbox are good.

The first talks about functioning/performance.
The second gives a more general evaluation.

In many situations, rade dobro is the more natural choice when talking about whether equipment is functioning properly.