NAG1 shift tuning: output-shaft rpm, not engine rpm

The NAG1 is a separate computer. On this window it is EGS52 in 2005–2006 and EGS53 from 2007. The PCM still needs a read. The TCM is the file that owns the shift schedule, the pressure request and the converter.

Do not start from the badge or the engine size. Start from the controller string and the part number in the TCM read.

1. Read both modules. PCM and TCM. Save the as-found files and the controller IDs before any edit. Confirm what the licence dialog asks for. A second computer is a separate question.
2. Record the hardware. TCM part number, OS ID, VCM Suite build, interface generation, valve body and converter if they are not stock. An aftermarket module may not open, and a modified valve body changes what the pressure table means.
3. Check the mechanical baseline. Fluid level and condition, DTCs, wheel speeds, actual rolling tire, axle coding and torque-model plausibility. A converter or clutch problem can look like a schedule problem.
4. Confirm writer support. Early EGS52 hardware and EGS53 definitions differ. A 2007 procedure is not automatically a 2005 procedure. Check the supported writer options for this exact controller.
5. Take a warm baseline in every mode you can select. Normal, Performance, Winter, WOT and AutoStick. Label the mode in the log. A Sport button does not prove which table is active.

Power goes engine, converter, turbine, gearset, output shaft. The TCM schedules on output-shaft speed because that is what the transmission knows. When a gear is engaged without internal slip, turbine rpm is output-shaft rpm multiplied by that gear's ratio. Engine rpm only approximates turbine rpm when converter slip is small.

Road speed uses the same geometry. For a 28-inch rolling diameter, a 3.06 final drive and 2,500 OSS, use this formula. mph = OSS × circumference(in) × 60 / (63360 × axle ratio) is about 68.06 mph. This does not need converter lockup. Inferring OSS from engine rpm does need a slip assumption.

1. Pick the gear you are leaving. The ratio belongs to the current gear, not the destination.
2. Divide the target turbine rpm by that ratio. The result is OSS for the request.
3. Multiply OSS by the destination ratio. Check the after-shift rpm in the new gear.
4. On a downshift, use the destination ratio. Check the landing rpm before the request is sent.
5. Check tire and axle data first. Actual rolling circumference, not the sidewall marketing diameter. A wrong axle ratio sets a ratio code and can stick the car in a limp gear.

The schedule is not one table. Normal, Performance, Winter, WOT and AutoStick each have an upshift and a downshift path. Some operating systems repeat pedal-axis breakpoints, and some add a speed offset to the cell.

A log that shows the shift later than the typed cell may be showing the offset, not a bad table.

1. Log the active mode. Use the selector and confirm the mode in the log. Do not assume the dashboard label names the table.
2. Compare request OSS with the cell plus the offset. Verify the interpolation between pedal breakpoints. A cell that is right at one pedal point can be wrong between two.
3. Make one small, localized, reversible change. If the request does not move, check mode, offset, cap, definition and write success before you make a larger edit.
4. Reconcile all modes with the objective. Every schedule that can be active has to agree. That does not mean Winter becomes identical to Performance.
5. Check the transitions. Into and out of WOT, into and out of AutoStick, and a kickdown while the converter is applying.

A shift point is a trade between wheel torque in the current gear and wheel torque in the next one at the same road speed. Peak torque is not the rule. The after-shift rpm has to sit where the engine still pulls, and the completion rpm has to stay under the limiter.

For a stock-spring 5.7, stay near the 5,500 rpm region. On a stock 2011–14 5.7 car, the wide-open shift sits near 5,500 rpm and the fuel cut sits near 5,800 rpm. Read both numbers from your file and your log.

Do not use these as cell values.

1. Read the engine fuel cut and the TCM limit. Write both numbers down. Do not infer either from a copied number.
2. Set a candidate OSS from the target turbine rpm. Use the ratio of the gear you are leaving.
3. Check the after-shift rpm. If it falls below the new gear's pull, the point is too early or too low.
4. Check completion, not just request. Log request, start and completion separately. Keep the completion under the actual limiter.
5. Keep the wide-open shift under the fuel cut. On stock springs, stay near 5,500 rpm. A 6,200 rpm shift is not a faster stock 5.7.
6. Do not raise the TCM limit to make a bad shift point work. A limiter is a protection, not a target.

Before you change a firmness table, identify what it contains. A table can be pressure, solenoid current, time, torque or a normalized coefficient. Confirm the unit and the sign in the help text and on a measured response. An inverse-acting current map cannot be tuned by "increase means more pressure."

1. Keep stock torque reduction while you establish the baseline. Confirm the engine delivers and reports a plausible torque. A pressure change on a bad torque report is a guess.
2. Confirm the table role and unit. Pressure, current, time, torque or coefficient. Check mA or amp, psi or kPa, and the sign. If the help does not settle it, measure the response before scaling.
3. Change one high-load region only. Read shift duration, turbine/output ratio, flare, tie-up and temperature. Less apparent engine flare can come from more torque reduction, not more clutch capacity.
4. Reject a change that makes a new flare, bind, harsh low-load shift, ratio DTC or escalating adaptation. Restore the file and check the hydraulics. Do not zero a protective limit to cover it.
5. Get the builder's requirements for a modified valve body or converter. No generic built-trans pressure numbers are printed here.

Lockup demand and actual slip are different. The common physical slip is engine rpm minus turbine rpm, but the Scanner sign can be the opposite. Check the sign. Negative coast slip can be valid.

Apply and release need hysteresis. Load, temperature and mode can override a visible table. Raising one apply table does not prove the converter locks at wide-open throttle.

1. Separate command from slip. Log TCC state, commanded slip and actual slip in the same region. Do not tune lockup from a single state flag.
2. Build apply and release with the actual convention. Check the load, temperature and mode overrides. A table that looks right at cruise can be ignored at heavy throttle.
3. Test a cam or high-stall converter at low rpm under load. Look for lugging or shudder before you delay lockup across the whole map. Keep warm cruise lockup where the hardware supports it.
4. Do not command wide-open lockup without the converter builder's approval. Clutch construction, capacity and heat differ from open-converter operation.
5. Validate the kickdown in the destination gear. Check landing rpm, torque reduction and converter release. Fix wheel-speed or ratio data before the schedule.

The TCM calculates output speed from the wheel-speed sensors. Incorrect tires or axle ratios can produce ratio errors or late shifts, and have led to unnecessary transmission replacement. Check the tire, the axle and wheel-speed plausibility before you diagnose the schedule.

If the TCM write fails

1. Stop. Save the exact error and the support log. Do not keep cycling the key or trying random files.
2. Restore the engine computer from the saved read. Keep the as-found file untouched. Work from a copy.
3. Confirm the hardware and OS. Some older operating systems are updated by the editor before a write. An aftermarket module may not open. A preflashed module is not the same as a stock one.
4. Update the transmission calibration before a second attempt. Use the supported writer option, a stable battery support and the correct ignition state.
5. If it fails again, stop and get support. A second blind attempt can turn a recoverable state into a bench job.

Validation is not one drive in Drive. Normal, Performance, Winter, WOT, AutoStick and a kickdown each need a before and after. Check request, start and completion separately.

1. Warm baseline first. Fluid at operating temperature. Record the mode, the gear and the converter state for every event.
2. Repeat the same route. A different road, tire pressure or load is a different test.
3. Compare request, start and completion. A request that moved but a completion that did not is a different problem.
4. Check the destination rpm on every kickdown. Then check the transition back into the next gear.
5. Check TCC release and apply separately. Do not let a shift event hide a converter event.
6. Send the same package for review. PCM and TCM reads, logs, channel config, IDs, mods, fuel and the exact changes. No VIN or customer name on a public example.