A perfectly tuned chassis with a badly geared box is a slow car. Gearbox tuning is the most overlooked and most undervalued lever in Forza Horizon 6. Get the final drive wrong and your car bounces off the limiter on every straight; get a single ratio wrong and you fall off the powerband at the worst possible corner. This guide walks through ratios, final drive, redline matching and the three special-purpose boxes — circuit, drag and drift.
Gearbox upgrades in FH6
Stock cars usually ship with 5, 6 or sometimes 7-speed boxes with fixed ratios. The transmission upgrade menu offers:
- Sport transmission: lighter, faster shifts, but ratios still preset
- Race transmission: 6, 7, 8, 9 or 10-speed, fully adjustable ratios and final drive
You cannot tune individual ratios until you have fitted at least the Race transmission. Sport boxes are only worth fitting if PI budget is tight and you can live with the stock ratios.
What the final drive does
The final drive is the single most important gearbox setting. It is a multiplier applied to every gear ratio. Raise it (numerically higher, e.g. 4.10 → 4.50) and you trade top speed for acceleration: every gear becomes shorter, your wheels turn slower relative to the engine, you accelerate harder out of corners but bounce off the limiter on long straights. Lower it (4.10 → 3.70) and you trade acceleration for top speed: longer gears, more theoretical top end, slower out of slow corners.
The rule: set final drive so you hit redline in your top gear at the end of the longest straight on the track you race. If you hit redline 100 metres before the brake zone, lower the final drive. If you never hit redline at all, raise it.
Ratio strategy 1 — wide vs close
Once the final drive is set, you adjust individual ratios. Two philosophies dominate:
Wide ratios: large gaps between gears, useful when your powerband is wide (turbo diesels, big NA V8s). The engine drops a long way between shifts but recovers because it pulls everywhere.
Close ratios: small gaps, useful when your powerband is narrow (high-revving NA fours, peaky turbos). The engine stays in its powerband on every shift but you need more gears to cover the same speed range.
Most race transmissions in FH6 default to a moderate spacing. For circuit racing with a peaky engine, bunch the middle gears closer together and stretch first and top. For drag, stretch every gear except the last to keep acceleration linear.
Ratio strategy 2 — corner-by-corner matching
The pro move: identify which gear you exit each corner in, then adjust that gear so the engine is exactly at peak power as you reach the apex. For a typical FH6 A-class car peaking at 6,500 rpm, that means making sure 3rd gear lands you at 6,200–6,400 rpm at corner-exit speed on a typical 2nd-gear corner.
This is finicky but worth 0.3–0.5 seconds a lap on a technical track.
Redline matching
Some upgrades — Racing cams, ECU tune — raise the redline. If you fit them but never re-tune the gearbox, you waste the new top of the powerband. Every time you change cams, exhaust, or the engine swap, redo your final drive first, then ratios.
Try EasyTune free — diagnostic in 30 seconds
Gearbox tuning has more variables than any other tuning page. EasyTune accepts a one-sentence description (“I bounce off the limiter at the end of the back straight”) and returns a targeted ratio change. Free at app.easytune.app.
How many gears do you need?
- 6 speeds: good for short technical tracks, low top-speed builds, drift cars.
- 7 speeds: the all-rounder. Most A and S1 builds run 7-speed.
- 8 speeds: useful when you have a very wide powerband and want close ratios in the middle plus a long top gear.
- 9–10 speeds: drag cars and very high-top-speed builds only. The PI cost is real and you almost never need that many on a circuit.
More gears is not automatically faster. Each ratio costs PI, and beyond 8 the marginal benefit drops off quickly except on Goliath-length straights.
Special case 1 — Drift gearbox
For drift setups, the dominant constraint is keeping the engine in its powerband while sliding at lower-than-normal road speeds. A 4-speed Race box (or a 5-speed with a very tall final drive) works best. Stretch first into a usable initiation gear, then keep 2nd–3rd very close so you can clutch-kick without falling out of power.
Special case 2 — Drag gearbox
For drag racing on the airstrip, every gear except the last should be short. Short first launches the car hard, short middle gears carry the engine through the powerband fast, and a tall last gear lets you keep pulling past 350 km/h. A 7 or 8-speed with a final drive around 3.6–3.9 and stretched 7th is the meta.
Special case 3 — Off-road / rally gearbox
Rally cars never hit theoretical top speed because they spend their lives at 30–40 percent throttle on mid-rev. Run a 6 or 7-speed with a moderately short final drive and close lower ratios. The goal is keeping rpm above 4,000 between corners.
Common gearbox mistakes
- Setting final drive for the dyno number, then complaining the car bounces off the limiter. Final drive is per-track, not universal.
- Forgetting to re-tune after engine upgrades. New peak power means new ideal ratios.
- Running 10 speeds because more is better. PI wasted unless you are on Goliath.
- Identical spacing on every gear. Real tracks have specific corner gear demands. Tune to the track.
Quick reference
- Final drive: hit redline in top gear at the end of the longest straight
- Mid-gear spacing: close for narrow powerband, wide for fat-torque engines
- Race transmission: 7-speed for most A/S1 builds
- Drift: 4-speed with tall final drive
- Drag: 7-speed, stretched last gear
- Always re-tune after engine work
Closing thought
Gearbox tuning is unsexy. It does not change how the car looks on the upgrade menu and it does not give you a single number to brag about on the leaderboard. But it routinely returns more lap time per minute spent than any other tuning page. Combine it with sound chassis work — understeer fixes, PI strategy, tire pressure — and you have a car ready for Top 100 Rivals.
Tune your gears. Find your redline.