Auton vauhti oli liian kova.

Because auton is the genitive singular of auto (car).

In this sentence, auton vauhti means the car’s speed or more literally the speed of the car.
The ending -n is one of the most common ways Finnish shows possession or a close relationship between two nouns.

• auto = car
• auton = car’s / of the car

So:

• auton vauhti = the car’s speed

In Finnish, a genitive noun usually comes before the noun it modifies.

So the pattern is:

• auton vauhti = the car’s speed
• literally: car’s speed

This is similar to English the car’s speed, where car’s also comes before speed.

Vauhti means speed, pace, or sometimes momentum depending on context.

In this sentence, it means speed. So auton vauhti is the speed of the car.

A useful point: vauhti is often used in everyday Finnish in a slightly broader way than just a technical measurement. It can refer to how fast something is moving in a practical, natural sense.

Yes. The subject is vauhti.

The full subject phrase is really auton vauhti (the car’s speed), but the head noun is vauhti, and that is why the predicate adjective is singular:

• Auton vauhti = subject
• oli = was
• liian kova = too high / too fast

So the sentence structure is basically:

[The car’s speed] [was] [too high].

Oli is the past tense of on, from the verb olla (to be).

• on = is
• oli = was

So:

• Auton vauhti on liian kova. = The car’s speed is too high.
• Auton vauhti oli liian kova. = The car’s speed was too high.

Liian means too in the sense of excessively or more than is acceptable.

So:

• liian kova = too high / too fast

It is not the same as English very.

For example:

• hyvin kova = very high / very hard / very loud, depending on context
• liian kova = too high / too hard / too loud

So liian adds the idea that the speed exceeded some limit or was more than it should have been.

Kova has several meanings, and Finnish uses it in many contexts where English uses different words.

Common meanings of kova include:

• hard
• tough
• loud
• strong
• high or fast in certain contexts

With vauhti (speed), kova means something like high or fast.

So:

• kova vauhti = high speed / fast speed
• vauhti oli kova = the speed was high

This is a normal Finnish expression, even though the most basic dictionary meaning of kova is often given as hard.

Because here kova is an adjective describing the noun vauhti.

After olla (to be), predicate adjectives are typically in the nominative singular when the subject is singular:

• vauhti oli kova = the speed was high

By contrast, kovaa is often an adverbial form, and it is commonly used with verbs of motion:

• Auto ajoi liian kovaa. = The car drove too fast.
• Hän juoksee kovaa. = He/she runs fast.

So the difference is:

• vauhti oli liian kova = the speed was too high
• auto ajoi liian kovaa = the car was going too fast

Both are natural, but the grammar is different.

It is possible to understand it, but liian kova is more idiomatic with vauhti.

Why?

• nopea means fast
• kova with vauhti means high / fast in a very natural collocation

So Finnish prefers:

• vauhti oli kova
• liian kova vauhti

Rather than:

• vauhti oli nopea

A native speaker is much more likely to use kova with vauhti.

Because Finnish has no articles like English a and the.

Whether something is understood as a car, the car, car, a speed, or the speed depends on context.

So:

• auto can mean a car or the car
• auton vauhti can mean the car’s speed or a car’s speed, depending on the situation

In a normal sentence like this, English usually needs the, but Finnish does not.

Yes, Finnish word order is fairly flexible, but changing it usually changes the focus or emphasis, not the basic meaning.

The neutral order here is:

• Auton vauhti oli liian kova.

This presents the sentence in a straightforward way: the car’s speed was too high.

You may also see other orders in special contexts, but the neutral learner-friendly version is the one given. So unless you have a reason to emphasize something else, Auton vauhti oli liian kova is the best form to learn first.

It is very close in meaning, but not exactly the same in structure.

This sentence literally talks about the speed:

• Auton vauhti oli liian kova. = The car’s speed was too high.

English often prefers a more verbal expression:

• The car was going too fast.

So in real usage, these can describe the same situation, but Finnish here is phrased as a statement about speed, not directly about the action of driving.

A more direct Finnish equivalent of The car was going too fast would be something like:

• Auto ajoi liian kovaa.

So the meanings are close, but the grammar and viewpoint are slightly different.