# Engine and Gearbox

See the [Maintenance Schedule](https://manual.rush.sr/maintenance/maintenance-schedule) for more information on when rebuilds are required.

We will collect various techniques and anecdotes for rebuilds in this section as we gather it from dealers.

For information on the GCU, see the [Shift Harness and GCU](https://manual.rush.sr/maintenance/electronics-and-wiring/shift-harness) page.

## Limp Mode Diagnostics

| Throttle Type                 | Diagnostic Steps                                                                                                                                                                                                                                                |
| ----------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Gen II — Drive-by-Wire**    | Connect the **Red** OBD connector to run diagnostics. If no fault codes exist but throttle is limited to 40%, check the Speed Emulator first. Quick check: in Neutral, rev the engine — if it does not rev beyond 6,000 RPM, the Speed Emulator is NOT working. |
| **Gen I — Throttle by Cable** | Connect the **White** OBD connector to run diagnostics. Limp mode at full throttle only = throttle is over-extending past ECM limit. Peak throttle percentage should not exceed 95% when viewed through OBD. Dash setup: 92% max.                               |

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**Ignition Fuse:** The 10A ignition fuse controls the ECM, Ignition Coils, O2 Sensor (not used in race configuration), and Pair Valve.
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## Recommended Engine Oil

Rush Auto Works currently recommends **Klotz KV1560R** (15W/60 racing oil). This replaced the previous recommendation following testing that showed meaningful improvements in wear protection.

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**Warm-up requirement:** When using Klotz KV1560R, the engine must be fully warmed up before entering the track. This oil is thicker at cold temperatures. Skipping warm-up accelerates wear.
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Amsoil Dominator 15W/50 is a well-regarded alternative used by a number of owners.

**Oil change interval:** Change at each event weekend, or per the service interval schedule.

See [Fluids](https://manual.rush.sr/maintenance/fluids) for the complete fluid specification list.

## Clutch Replacement

An important note; when tightening and using **blue** loctite on the clutch, do not fill the motor with oil right away as it will cause the loctite to have trouble bonding. Leave the bolt torqued and the motor dry for some time (at least 24 hours) to allow the loctite to bond properly.

Failure to do this can cause the bolt to come loose, and will cause shift issues and failure of the clutch to fully engage.