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Upgrade reference /drivetrain-parts

Drivetrain Parts (Diff / Trans / Driveline / Clutch / Flywheel)

PI traps live here. Race-tier on everything stacks 15–25 PI you usually want elsewhere.

What it does

The five drivetrain parts — Differential, Transmission, Driveline, Clutch, Flywheel — are individually small PI but stack quickly. The community rule of thumb across ForzaFire / kboosting / ggwtb is: don't Race-tier all five by default. The combined PI hit is 15–25 points, and that's budget that almost always returns more on tires or weight.

Differential is the only one of the five that's usually worth Race-tier — it unlocks the full Accel + Decel sliders on both axles and the AWD center-balance slider. Without it, you can't do the corner-exit work the tune reference describes.

Transmission PI cost *scales* with how much power you've added. The Sport transmission at A-class might be cheap; the same Sport transmission at S2 with 700 HP costs noticeably more. Re-check after engine upgrades.

Driveline is the underrated value upgrade — small PI, real rotating-mass weight reduction, and often the cleanest fine-tuner when you're hunting the last few PI points before the class ceiling.

Clutch upgrades are a PI trap unless you actually use Manual-with-Clutch input. If you're on Automatic or Manual, the clutch upgrade does almost nothing.

Flywheel reduces rotating mass — like driveline, it's a quiet weight reduction. PI cost is usually low and worth it on grip / drift builds.

Options

Race differential
PI 3–8
Best for
Anyone who plans to actually tune their car
Tradeoff
PI cost is small; the unlocked tuning sliders are the entire reason to upgrade
Sport transmission
PI 2–5
Best for
B/A class — unlocks Final Drive only, which is most of what you need
Tradeoff
No individual gear ratios
Race transmission
PI 5–12 (scales with power)
Best for
S1/S2/R where powerband matching matters
Tradeoff
Often better spent on tires/brakes at lower class
Race driveline
PI 2–5
Best for
PI fine-tuner; rotating-mass weight reduction
Tradeoff
Almost always worth it on grip builds
Race clutch
PI 2–5
Best for
Manual-with-Clutch input users only
Tradeoff
Effectively wasted PI on Auto/Manual without clutch
Race flywheel
PI 2–5
Best for
Most grip and drift builds — small PI, real benefit
Tradeoff
Engine can feel snappier — pair with rev-matching habit

Decision rules

  • 1.Race differential is the only must-have of the five. Everything else is a budget call.
  • 2.Don't install Race clutch unless you drive M/C — it's wasted PI.
  • 3.Re-check transmission tier AFTER engine upgrades — its PI cost scales with power.
  • 4.Use Race driveline / flywheel as PI fine-tuners when you're close to the class cap.

Traps

Race-tier every drivetrain part because they're "small"
Why  Stacked, the five parts can eat 15–25 PI that wins more elsewhere
Instead  Differential mandatory; the rest are budget calls
Race clutch on Automatic transmission input
Why  The simulation doesn't model your shifting; the upgrade does almost nothing
Instead  Skip it; put the PI into tires or weight

Build smells that point here

  • Race-tier on all five drivetrain parts
    Keep Race diff; downgrade transmission to Sport at B/A; skip Race clutch on non-M/C input. Reclaim 5–15 PI.
  • Race clutch on Automatic or Manual input
    Skip it — the simulation doesn't model your shifting; the upgrade does nothing.

After the install — tune it

/tune/differential

Related

Weight ReductionDrivetrain Conversion (FWD ↔ RWD ↔ AWD)