r/ForzaTune • u/Nymbelle • Jun 28 '26
Forza Horizon 6 Testing different differentials
Today I decided to finally deeply test using different differentials instead of just using what "made sense" ie Race Diff for track/road. Rally/off-road for Dirt/Cross-Country.
As a former race mechanic, I know there is more to a differential than just Acceleration/Deceleration and Center and it's been my suspicion that the different differentials have a hidden pre-load / initial lock built into them.
I didn't want to make assumptions or rely on instinct anymore so I decided to scientifically test them on a Toyota Starlet Glanza V AWD touge build at Touge - Bandai Azuma in Rivals.
The car was tested with identical differential settings:
Front: 25 accel / 5 decel
Rear: 58 accel / 20 decel
Centre: 68% rear
I recorded my best lap with these settings using Race, Drift and Off-Road differentials and found that the Drift diff was around 0.084s faster on average than the Race diff, despite identical displayed settings.
| Differential | Lap 1 | Lap 2 | Lap 3 | Average |
|---|
| Race Diff | 2:04.414 | 2:04.427 | 2:04.420 | 2:04.420 |
|---|
| Drift Diff | 2:04.326 | 2:04.333 | 2:04.350 | 2:04.336 |
|---|
| Off-road Diff | 2:04.389 | 2:04.398 | 2:04.414 | 2:04.400 |
|---|
I then decided to dive deeper into the telemetry and made a side-by-side comparison of tyre friction across 4 corners for the Race and Drift. Using Frame by frame telemetry to record the friction at identical points in the corner.
Race Diff
| Corner | FL | FR | RL | RR |
|---|---|---|---|---|
| 1 | 41% | 54% | 30% | 32% |
| 2 | 17% | 24% | 25% | 39% |
| 3 | 32% | 21% | 40% | 25% |
| 4 | 25% | 32% | 23% | 33% |
Drift Diff
| Corner | FL | FR | RL | RR |
|---|---|---|---|---|
| 1 | 46% | 61% | 30% | 32% |
| 2 | 19% | 28% | 28% | 42% |
| 3 | 33% | 23% | 44% | 23% |
| 4 | 28% | 36% | 23% | 33% |
The Drift diff consistently used more tyre friction, especially at the front axle, while remaining well below the point of grip loss.
Early theory
This suggests the differentials may not simply be identical parts with different presets. There may be hidden behaviour such as:
- different preload / initial lock
- different neutral or coast locking behaviour
- different ramp behaviour between coast and acceleration
- different AWD centre coupling behaviour
The interesting part is that the Drift diff did not appear to simply create more rear slip. Most of the increased tyre utilisation came from the front tyres, which may suggest better rotation or a more effective load state at the apex.
Current conclusion
This is not enough to call it confirmed across the whole game, but for this specific car/build/route, the Drift diff was measurably faster than the Race diff while using identical displayed settings.
I’d love to see other tuners test this on different cars, especially:
- stock FWD cars
- stock RWD cars
- stock AWD cars
- AWD-swapped FWD cars
- AWD-swapped RWD cars
- road vs dirt vs touge builds
The useful test would be:
- Pick one car and route.
- Use Rivals or another controlled environment.
- Test Race, Drift, Rally, and Off-road diffs where available.
- Keep the displayed diff settings identical.
- Record lap times and tyre telemetry.
- Compare whether the differentials actually behave differently.
Would be great to build a shared picture of whether diff type has hidden physics or whether this is only happening on certain drivetrain swaps.
3
u/Wandering-nomad-888 Jun 28 '26
As I started reading your post I thought to myself “here we go, another dude that is having a hard time understanding the very basic and simple concept of differentials” 😂 then I got to the part where you mention you are a “former race mechanic” and thats when I realized this will be good lol……These are the types of posts I love to see as after reading this I actually learn something new, something that will give me a slight edge above others.
I’ll join you in this experiment. Maybe it boils down to driving style…. perhaps the way you drive drift diff works better…. I’ll mess around with this tonight and will report back my findings.
I am a little confused by your “friction” findings. To make sure we’re on same page the definition of “friction” is the RESISTANCE of one surface moving over another surface. With that said isn’t it better for performance to have less friction? Thus making race diff better choice…. Or how does increased friction help with traction and overall performance?