More Power = Thicker Diffs Oils?

[obessedwithrc]

Is there a "rule of thumb" for changing differential oil when increasing or decreasing power?​

• When running an MT410 on 4s, run the stock oils
• When running an MT410 on 6s, double the oil viscosity?

Yes. I know that most of tuning comes down to the specific use-case (stunting vs. racing), driver preferences, and other conditions like ambient temperature, terrain, etc. That said, I'm curious to know, in general, if moving up in power from let's say, running 4s to 6s, if there is any kind of "rule of thumb" or "ideal approach" to changing differential fluids to handle the additional power.

Even "off the cuff" answers, i.e., "I increase f/r by 50% and center by 100% when I move up in power" would be super helpful.

As another example, I am running an SCT410SL on 3s a basher. Obviously the stock setup (oils specifically) were chosen for 2s power. How would you approach optimizing the diff fluids in this specific case? And in general?

 

[Matthew_Armeni]

I'm assuming that when you go from 4s to 6s you're not re-gearing or changing motors? If you're taking your 4s powered truck that's been paired with a 4s kv motor and geared for ~35-45 mph and swapping in a 6s battery with no other changes, your diff oils will probably feel a little light. You'll probably want to go up in the center, maybe the front.

 

[Leonoff.A]

For mt410 stock oil 100 100 50 no problem for 4 or 6s with same setup (change only battery). I run 4274 2200kv with 17t pinion both 4 and 6... but for track chassis very are oil's like 10 10 5, I think it better to use something thicker with 6s

 

[RC-Steve]

My daughter's mt410 I run 50/500/30.
My MT48 2.0 I run 10/500/30.
My Kraton and Sledge with 1/6th power systems in them I run 50/500/50.
My Kraton XL I run 50/200/50. Higher than 200k in the center causes the long wheel base truck to spin out.

500k in the center seems to be the limit, beyond that the truck turns into a spin out queen.

My diff setups are specific to dirt parks. I'm not a racer.

 

[Klappars]

I think it’s really a case of observing the way the car drives and trying different setups to see if it’s better or worse or solves a problem.

Such as , if the centre diff oil is too thin, with too much power, you would see the front wheels spin up a lot, the power is bled to the front, more so than the rear.

If this causes undesired behaviour such as not enough power to the rear to kick the back end out or pull wheelies, then go for thicker oil, but don’t overdo it otherwise you can make the vehicle hard to drive and less compliant to different traction surfaces and driving style.

The front differential oil affects the steering on and off power.

Too thin for the power level, and you may find the on power steering is lacking, pushing wide, understeering. You might see the inside front wheel spin up too much.

The rear differential oil affects how how the rear end puts the power down, too thick and it will want to spin out readily and be tricky to drive on low traction surfaces. Too thin (for the power or traction level) and the inside wheel is likely to spin up out of control and be less predictable on high traction surfaces.

To conclude, run the truck with stock diff oils, observe how it drives, bearing in mind the traction of the surfaces you are running on and your tyre choice, then tune the diffs according to how you want the vehicle to drive. Somebody who wants the vehicle to be very agile and handle neatly would generally want thinner oils, while someone who wants it to oversteer and pull stunts would want thicker oils, with the trade off being that the vehicle is likely to be harder to drive if the traction isn’t there and it may feel more ‘numb’ to drive.