meaning of “grunt” when it comes to towing

Question

The title of the humorous story is "The Sun got stuck"

“I don't suppose you could give us a tow, could you, sister?”

Luna's eyebrows shot up, “How? With what? The sun's 400 times larger than the moon, and even if I could give you a tow, it'd take me 8 light minutes to get there! And besides, I may have lowered it and put a supercharger in, but I'd never have enough grunt to tow it! Sorry, sis, but you're on your own. You can fix it, can't you?”

I tried the usual (Wiktionary, Merriam-Webster, The Free, Dictionary.com) and none of the definitions (foot soldier, sound, menial worker, fish, dessert), seem to match this kind of usage. What does grunt in this context mean?

Answer 1

From the Oxford Dictionary:

3 [mass noun] British informal mechanical power, especially in a motor vehicle: what the big wagon needs is grunt, and the turbo does the business

Grunt is being used to describe pulling (or towing) capability. I found it in this article relating an entry in a tractor pulling competition:

He says it is about having the tractor with the most grunt, but adds that a lot of skill is also involved.

Answer 2

In this context, grunt means power or force. In the context of engines in general, grunt often refers to the amount of torque that the engine can produce.