Im really new to nitro rc and I have a 2wd off road stadium truck. Some one told me that I should fill the diff with diff oil to make it handle better.. so how does it work?

1. How to understand the viscosity rate? The highest rating is the thickest?

2. How to know what viscosity to use? Thin oil is for? Thick oil is for?

Thanks in advance!

diff oil and shock oil is silicone oil. the viscosity (sometimes in WT's) if how much it resists to flow. Basically, the more the WT, the thicker the oil. So 40WT is thicker then 20WT for example. There are other ways or measuring the viscosity but its the same principle.

in a gear diff, the oil slows the action of the gears. Diffs in rc cars are 'open' diffs which means that power is put to the wheel with less traction. So using thicker oil counteracts this and the diff feels more "stiff" giving more power to the wheel with traction..

if youve ever taken a real fast and shard turn, one wheel might have "ballooned". Thats because the diff too easily gave power to the wheel with less traction, and the centrifugal force made the rubber expand.

Same thing with shocks, thicker oil slows the shocks and thinner oil makes the action quicker, more 'bouncy'.


I dont know what oil to use in a firestorm so ill let someone else add that in.

if you are talking about your firestorm 10t, it does have a sealed diff, so all you need to do is pull it out, clean out the grease, and refill it with diff oil... start with 1000wt and see how you like it, if it still unloads too easy, go up in Wt.. higher is thicker... the thicker the oil the more you will slow the diff action, you need some diff action to go around corners well, so too thick will detract from handling as well...

Differentials are meant to improve your turning capabilities. The way a differential works is when you go through a corner, your outside tire has more distance to cover than your inside tire. Your differential lets your outside tire spin more and your inside tire spin less. There are a few different ways to set up a differential, depending on whether it’s a 2wd or 4wd car, and what track or what type of racing you are doing, but if you are driving a rwd truck on dirt off-road…

Lets say you don't have a differential, or you lock your differential. This will reduce your cars’ off power steering drastically. Your inside tire will drive more than it should, and your outside tire won't be driving enough. Both will cause your car to push. You can get through corners faster by breaking traction with your rear wheels, but this will make the car very unstable and you will be spending most of your time spinning out. If you get out of shape while going down a strait, it will be very hard to recover from. Your car will spin out or drive off course.

Now lets say you are using your car with a geared diff and no oil or grease. One advantage to this is amazing off power steering. Your inside and outside tires get to roll as much as they want, and it gets you through the corner fast. This is not good for your on power steering. If you are driving through a large sweeper or exiting a corner, it's almost like trying to fly a high powered rocket with no guidance system. You are going to be very inconsistent, and there is no telling where your car is going to point. If you get out of shape going down a strait and your car starts to spin out, it will turn sideways, but then your rear tires will quickly spin at different speeds and your car will try to snap back to whatever direction the cars' momentum is taking it (fishtailing).

Using the general info I just gave you, you want to find something in the middle that works with what size track you are running on, and your driving style. If it's a shorter track with lots of turns, you might want to use thinner oil. I would start with 3000wt, and go up from there. If it's a larger track with larger turns, you might want to use something like 10,000wt - 20,000wt. Tightening and loosening a ball differential does the same thing, but you only need to turn one screw instead of taking the car apart. A geared differential has an advantage because it can be as loose as you want it. A ball differential can only be so loose, before it becomes too loose and starts to slip. It usually doesn’t need to be this loose on a 1/10 vehicle.

Hopefully this helps a little more, and hopefully my info is all correct.

Thanks so much for all your inputs!
Helped me a lot understanding how to set up my diff..