Lesson 4: Differentials

Lesson 4: Differentials

Now it's time for probably the most interesting part of your vehicle, differentials! A 4WD Losi comes with three gear differentials: Front, Center and Rear. The TLR 22-4 comes with ball differentials and are out of scope for now. There is not much what you can change on gear differentials except the fluid. The diff oil decides how your truck behaves itself in corners and driving in a straight line. So, it's wise to fill your differentials with the right oil. However, how does the truck respond on the different thicknesses of fluid?


1. Estimate the track

First, it is good to know that you have to estimate the track situation. Most of the tracks are changing during the day when there is so much action. Starting a flat track and ending on a bumpy track means a lot of mechanic skills between the races. However, this is really a challenge because changing the diff fluids requires a lot of time. Try to setup your differentials before you drive. By taking your time to adjust your differentials, you will see that your car is getting faster and faster! Observing your car is very important and writing down your experiences within a setup sheet can help to make some decisions much easier.

2. Front Differential

  • Lighter oil: Standard your Losi comes with 5000 oil in front and is fine for all-around driving. Thinner oil will give you the ability to get more steering off power but you will loose on power steering. However, do not put in too thin oil because it can make your diff inconsistent. Choose thinner oil when your are driving on a technical and bumpy track.
  • Thicker oil: When you are driving on a large track it is wise to choose a thicker oil. This because your are getting more steering during on power. The opposite is that thicker oil is resulting in a less off power steering. So, choose thicker oil when you are driving on as fast and big track. This is also the choice for bashers.

3. Center Differential

  • Lighter Oil: Lighter oil in this diff will cause a slower truck as it will limit forward acceleration. It will also be able to unload the drivetrain easier. Thinner oil will reduce on power steering, in other words it reduces over steer in your truck. This setup is great while your are driving on a short and technical track.
  • Thicker Oil: More acceleration and better on power steering when you put thicker oil in this differential! However, it decreases off power steering so this is not the choice for short and technical tracks. Are you a basher or driving on large tracks? Put thicker oil in center!

4. Rear Differential

  • Lighter Oil: Driving on a short track it is wise to put thinner oil in your rear differential. This because it gives the truck more steering in the middle of the corner. It also has more side traction so it can help you a lot to get better out of tight corners.
  • Thicker Oil: Forward traction is important when driving on a field or large track. That is exactly what thicker oil does when you put it in your rear differential. The opposite is that it gives the truck less steering in the middle but for large areas, this isn't important.

5. Last words

The different weight of viscosity can change the behavior of your truck drastically. The different combinations of oil have a direct effect on how the car is handling in corners, acceleration, bumps and the way it releases the drivetrain while off power. Normally thinner oils will make the car easier to drive. On slippery and bumpy tracks thinner oils are better. On smooth high traction tracks thicker diffs will be better. Thicker diffs give more acceleration, more corner speed, and help to make the car more stable on a high traction surface. On special tracks, that are really smooth and high traction, asphalt like, the car will be a lot more stable and fast in the corners if all diff oils are made thicker.

The standard diff weight in all 4WD TLR / Losi is:  

  • Front: 5000
  • Center: 7000
  • Rear 3000

There is only one exception on above weights and that are the recommendations for the 8th scale Truggy models. This because these cars are having a completely different geometry (wide with huge wheels). The default Truggy setup is:

  • Front: 10000 (7000 for nitro truggy)
  • Center: 10000
  • Rear 7000

Above diff setups are a very good starting point for every driver and situation. Nevertheless, this is a great tuning aid, so try different combinations to get the best out of your car!

This tutorial is part of the five 'Back 2 the Basics' lessons written by:
Todd Hodge (Surface Category Development Manager Team Losi Racing / TLR)
Ralf van Hattum (TLR Team Driver and founder Planet Losi Racing)

All Back 2 the Basics lessons can be found here.

Lesson 5: Sway Bars
Lesson 3: Steering

Good to know...

All information is copyrighted by Planet Losi Racing. We are a non-official Losi page and all information isn't initiated by any manufacturer.


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