Triple Diff Basics
 

TRIPLE DIFF BASICS
(This article is from RCDRIVER)
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Tuning your Diffs
Most diffs are designed to be filled with viscous silicone fluid, which alters the diff’s tension, i.e. makes it “LOOSE” or “TIGHT”. What this is really doing is changing the diff’s “limited slip” properties. A loose diff will send more power to a wheel that loses grip, robbing valuable power to the wheels that have traction.
Some general rules that can be applied for diffs.
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GENERAL DIFF RULES:
A looser diff provides more traction and will enable vehicle to work better on rougher surfaces. A stiffer diff works better on high grip conditions and improves acceleration and throttle response.
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FRONT DIFF:
A good starting point for 1/8 scale biggies and truggies, is to fill the front diff with 7k wt. silicone fluid. Using thinner fluid will loosen the diff’s action, improving steering response, but will also tend cause a decrease in stability under hard acceleration, as the front wheels will more likely to pull to one side or the other in reaction to the chassis transverse weight and to irregularities in the running surface. Thicker fluid enables the front wheels to pull harder and with greater stability, and on-power and high-speed steering will improve, but you will lose some off-power steering response, especially in slow turns. Try to use fluid no thinner than 3k or thicker than 10k in the front diff.
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CENTER DIFF:
Buggies- start by filling the diff with 10k wt silicone. This usually provides a good combination of acceleration and stability. If your vehicle leans toward over-steer when exiting turns, using thinner fluid such as 5-7k in the center diff will send more power to the front wheels, allowing them to pull harder. At the same time, drive to rear wheels will be slightly diminished. The shortcoming is the overall acceleration will be reduced, as more power will be sent to the unweighted front wheels, while less goes to the rear wheels.
A looser center diff will improve off-power steering response, as it reduces wheel-slip, thus inhabiting understeer, or push, by allowing the front & rear diffs to function more independently during cornering.
A tighter center diff sends more power to the rear wheels , thus allowing the car to be “ steered” more by the rear wheels, increasing on-power steering.(but at the loss of stability on slippery surfaces)
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Truggies- It is not uncommon to use 20k or even 30k silicone fluid in a truggies center diff to compensate for the extra heft and rotating mass of the tires. If the tires tend to expand hugely during acceleration, thickening the fluid the front diff and center diff is often a remedy. Some drivers have run up to 20k diff fluid in front diff to reduce tire expansion.
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REAR DIFF:
Of the 3 diffs found in the vehicles, the rear is run the loosest. This is done in a effort to achieve maximum traction from the rear wheels- during acceleration as well thru the bumps. Most racers fill their diffs with 1k-3k, but no more than 7k. Using anything thicker will create a condition of oversteer when exiting turns, making the vehicle the vehicle difficult to control in almost any conditions.
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This article was originally written: by Frank Masi of RC-Driver
Copied by: Shayne Richardson

Great info. let's make it a sticky..

dont know if this is usefull:

DIFF OIL
THICKNESS CHARACTERISTICS
Front
Thinner
• Increases steering into corners (off-power)
• If oil is too thin the steering may become inconsistent,
especially it can lose forward traction (and steering)
during acceleration out of corners
Thicker
• Increases stability into corners during braking
• Increases steering on-power at corner exit
Center
Thinner
• Front wheels unload more during acceleration
• Decreases on-power steering (reduces oversteer)
• Easier to drive on rough tracks
• If a high-power engine is used you could waste too
much power and sometime “cook” the oil in the center
differential because it “overloads”
• More off-power steering
Thicker
• More all-wheel drive effect
• Better acceleration
• Increases on-power steering (reduces understeer)
• Better suited on high-bite, smooth tracks
• Car can be more nervous to drive especially if a high
power engine is used - you might need to be smooth on
the throttle
Rear
Thinner
• Increases cornering traction
• Increases steering into corner
Thicker
• Decreases rear traction while cornering
• Reduces wheelspin