Nickelodeon Kart Racers 3: Slime Speedway

Easily the worst grind out of any of the previous titles.

I finished every Time Trial ghost, all of Challenge Mode, won 40 cups, and STILL needed about 9500 slime tokens to unlock the rest of the stuff in the store.

Arena no longer gives any tokens and losing a challenge offers none either, so both boosting methods from last game no longer work. Also no bonus for playing online. You can earn up to 40 coins in local multiplayer but doing a race is incredibly slow compared to the solution.

The most amount of coins you can earn by yourself is 10 tokens per race, 40 tokens per cup, and up to 30 bonus tokens at the end of a cup...but you'll rarely get any bonus tokens.

What was discovered was that when you fail a challenge you keep any tokens earned. There is a Rocko challenge named "Keeping up with The Bigheads" in the second section of Challenge Mode that is for completing a race on Nature-O-Rama without touching the walls or over rough terrain.

The strategy is to reverse after the countdown and collect the five tokens behind you, wait for them to respawn, grab them again to get to 10 and then slam into the wall right next to you to fail the challenge but bank the tokens. Repeat.

It will take a long time, but (at the time of writing) this is the most optimal way of grinding this out. If a better way is discovered, I can update the solution. Sadly, you can't equip crew members to make this easier.

HAPPY GRINDING.

Something to add to QueenVercua's guide is that I have calculated the total amount of Slime Tokens you need to bank to buy everything in the Garage. Here's the complete list of all the sections and how much there is.

Drivers - 2,920 Total Tokens
-150 Tokens * 6 = 900
-160 Tokens * 5 = 800
-170 Tokens * 6 = 1,020
-200 Tokens * 1 = 200

Karts - 1,420 Total Tokens
-105 Tokens * 2 = 210
-115 Tokens * 4 = 460
-125 Tokens * 6 = 750

Bikes - 470 Total Tokens
-105 Tokens * 1 = 105
-115 Tokens * 1 = 115
-125 Tokens * 2 = 250

Wheels - 1,980 Total Tokens
-20 Tokens * 24 = 480
-30 Tokens * 30 = 900
-40 Tokens * 15 = 600

Exhaust Pipes - 1,645 Total Tokens
-15 Tokens * 24 = 360
-25 Tokens * 22 = 550
-35 Tokens * 21 = 735

Paint Jobs - 2,215 Total Tokens
-45 Tokens * 14 = 630
-55 Tokens * 17 = 935
-65 Tokens * 10 = 650

Chiefs - 1,010 Total Tokens
-90 Tokens * 3 = 270
-100 Tokens * 3 = 300
-110 Tokens * 4 = 440

Engineers/Mechanics - 1,170 Total Tokens
-45 Tokens * 10 = 450
-55 Tokens * 6 = 330
-65 Tokens * 6 = 390

GRAND TOTAL: 12,830 Tokens to buy everything in the Garage, and that's a ton! Yeah, almost 13K!

First things first, though: I recommend you focus on all the other achievements before tackling this one, or at least as much as you can thanks to the online multiplayer being dead for this game. By the time you've gotten them, you'll have banked up a nice chunk of Tokens to buy a lot of stuff from the Garage, but nowhere near enough to get everything.

Using QueenVeruca's guide, you can just keep on replaying the Challenge again and again, racking up 10 Tokens per race quickly. Just be sure that to make the process go faster, keep mashing through the menus and track introductory scenes since they waste time, and then go from there. Just be sure to not get the boost start when the countdown begins.

You'll also notice that this achievement has a high ratio. This is simply because it is a massive grind and you'll need to do this an abundant amount of times. Trust me... it is going to be insanely boring and repetitive, but at least it's simple to do. If the dialogue and/or music get too repetitive for you, you can always turn them off and play something in the background as you collect the Tokens.

That's all I wanted to add on the matter. Hope this elaborates further.