A table that works differently
Most NSP tables have two numeric axes and you read a value where they cross. The Auto Mode Shift Point table breaks that pattern. Its left axis is locked to the Auto Shift Point Axis, and instead of numbers it holds gear changes written as "from gear, to gear". An entry of 1 -> 2 means a shift from first to second. 3 -> 2 is a down-shift from third to second.
The value in each row is the shift point for that change, expressed in whatever you've chosen as the Main Shift Point Variable: engine RPM, driven wheel speed, driveshaft speed or driveshaft RPM. If you enable the top axis (usually load or throttle), each shift can move with how hard you're driving.
The table only exists when automatic shifting is turned on. If the Auto Shift Option is set to Auto Disabled, you won't see it.
How the ECU uses it
While auto shifting is allowed by the gear selector position, the ECU asks two questions about the current gear, over and over:
- Should I go up? If the up-shift from the current gear is listed on the left axis, the ECU looks up its value. When the Main Shift Point Variable rises above that value, it requests the up-shift.
- Should I go down? If the down-shift from the current gear is listed, the ECU looks that value up too. When the variable falls below it, it requests the down-shift.
Say you're in third on a transmission using speed as the variable. The ECU checks for a 3 -> 4 row and a 3 -> 2 row. If 3 -> 4 currently works out to 60 mph and you're doing 62 mph, you get fourth. If you slow to below whatever 3 -> 2 calculates to, you get second.
What you list controls what it can do
A shift that isn't on the left axis simply never happens automatically. That's useful. If you want the car to auto-shift through third but never pick fourth on its own, list 1 -> 2, 2 -> 3, 3 -> 2 and 2 -> 1 and leave the rest out. A manual request from the driver, such as a paddle, can still select fourth.
You only need single-step shifts. A four-speed needs six rows: three up and three down. You don't add 1 -> 3 or 4 -> 2. If you want the ECU to jump gears when it makes sense, tick Allow Gear Skip. It then looks at consecutive rows, and if the car has already passed both the 2 -> 3 and 3 -> 4 points, it goes straight from second to fourth.
The mistake that makes a transmission hunt
Every up-shift drops engine RPM. If the down-shift point for the new gear is above where RPM lands, the ECU up-shifts, sees RPM under the down-shift point, down-shifts, sees RPM over the up-shift point, and repeats. The result is a gearbox cycling between two gears.
- With engine RPM as the variable, work out the RPM after each up-shift and make sure the matching down-shift point sits well below it.
- With a speed-based variable (driven wheel speed, driveshaft speed or driveshaft RPM), it's simpler: each down-shift point must be lower than the up-shift point it pairs with. If
1 -> 2happens at 30 mph,2 -> 1has to be under 30 mph.
Leave a real gap, not a token one. A few hundred RPM or a few mph of hysteresis keeps small throttle changes from triggering a shift.
Calculating engine RPM shift points
Logs and road testing will get you there eventually, but a little arithmetic gets you most of the way before the car moves.
Up-shifts
At full load, a gasoline engine usually makes its best acceleration by revving as high as it safely can, so the full-load up-shift points go just under the Main RPM Limit. Part-load up-shifts are where the art is. They depend on how the car should feel, and they're tuned by driving. Use this to sanity check each one:
RPM after shift = shift RPM × current gear ratio ÷ next gear ratio
Down-shifts
Decide what RPM you want to land on in the lower gear, then work backward:
down-shift RPM = landing RPM × current gear ratio ÷ lower gear ratio
Don't aim to land right under the up-shift point. If you do, the next time the driver gets on the throttle the transmission has to up-shift again almost immediately. A slightly less ideal gear with no extra shift is usually quicker.
Worked example: 4L80E-style ratios
Take a four-speed with ratios of 2.48, 1.48, 1.00 and 0.75, a Main RPM Limit a little above 6,000 rpm, a full-load up-shift at 6,000 rpm, and a down-shift landing target of 5,000 rpm.
| Shift | Math | Shift point | Hunting check |
|---|---|---|---|
1 -> 2 | Up-shift near the limit | 6,000 rpm | Lands at 6,000 × 1.48 ÷ 2.48 ≈ 3,580 rpm |
2 -> 3 | Up-shift near the limit | 6,000 rpm | Lands at ≈ 4,050 rpm |
3 -> 4 | Up-shift near the limit | 6,000 rpm | Lands at 4,500 rpm |
4 -> 3 | 5,000 × 0.75 ÷ 1.00 | 3,750 rpm | Below 4,500, so no hunting |
3 -> 2 | 5,000 × 1.00 ÷ 1.48 | ≈ 3,380 rpm | Below 4,050, so no hunting |
2 -> 1 | 5,000 × 1.48 ÷ 2.48 | ≈ 2,980 rpm | Below 3,580, so no hunting |
That's a full-load, race-style table with no load axis. To make it streetable, turn on the top axis, keep these numbers in the full-load column, and fill the lighter-load columns with lower values that you refine on the road.
Calculating vehicle speed shift points
If you've calibrated the vehicle speed sensors and the gear ratio settings, the ECU already knows how fast the car goes per 1,000 rpm in each gear. Gear ratios have to be learned with the torque converter locked, which is what dyno mode is for. The shift speed is then:
shift speed = shift RPM ÷ 1,000 × gear ratio setting for that gear
Use the current gear's setting for up-shifts, because the goal is to avoid over-revving the gear you're in. Use the lower gear's setting for down-shifts, because the goal is to land at your target RPM in that gear.
Continuing the example, suppose the gear ratio settings work out to 7.5, 12.6, 18.6 and 24.8 mph per 1,000 rpm:
1 -> 2: 6,000 ÷ 1,000 × 7.5 = 45 mph2 -> 1: 5,000 ÷ 1,000 × 7.5 = 37.5 mph2 -> 3: 6 × 12.6 ≈ 76 mph, with3 -> 2at 5 × 12.6 = 63 mph3 -> 4: 6 × 18.6 ≈ 112 mph, with4 -> 3at 5 × 18.6 = 93 mph
These numbers assume a locked converter. A slipping converter lets the engine spin faster than road speed suggests, so real up-shifts need to happen at a lower speed than the math says. Either account for slip or treat the calculated values as a ceiling and tune down from logs.
Troubleshooting shift points
| Symptom | Usually |
|---|---|
| Transmission cycles between two gears | Down-shift point sits above where RPM or speed lands after the up-shift |
| A gear is never selected automatically | That shift isn't listed on the left axis |
| Hits the limiter before shifting | Speed-based points calculated without converter slip, or gear ratio settings not calibrated |
| Skips a gear unexpectedly | Allow Gear Skip is ticked and two consecutive shift points are close together |
| Table missing in NSP | Auto Shift Option set to Auto Disabled |
Related settings: shift point load, RPM shift point, shift inhibit and outputs for gear. The overview lives in transmission control.
Shift point FAQ
Should I use RPM or vehicle speed for shift points?
Speed-based variables are easier to keep stable because the hunting rule is simple. RPM can be more intuitive for race cars. Either works if the down-shift points are placed correctly.
Do I need a row for every possible gear change?
No. List the single-step shifts only, and use Allow Gear Skip if you want multi-gear jumps.
Can the driver still shift manually?
Yes. A paddle or tap request can select a gear even if that shift isn't listed in the table.
