Overview of the Sonoma Race Weekend
Following the opening round of the Zenith Racing Series at Sonoma Raceway, Sebeco Motorsport has continued its review of the driveshaft-related issues that affected a number of ZP2 competitors over the course of the weekend. Since Sonoma, Sebeco’s focus has been on further understanding the contributing factors, developing updates, and further validating those updates through additional on-track testing.
Sonoma also provided important clarity in a demanding endurance-racing environment and reinforced the overall strength of the platform and category. The event featured nine Sebeco entries across five highly competitive teams — Round 3 Racing, Nimbus Racing, Automatic Racing, Random Vandals Racing, and Stratus Racing — and the racing throughout the field was incredibly competitive. Just as importantly, the weekend generated valuable data that is already shaping the next phase of Sebeco’s endurance development work, while also providing encouraging development value for the next-generation platform currently in progress, including Sebeco’s turbo package project.
One of the clearest findings from the post-event review is that the driveshaft-related issues are primarily an endurance-racing consideration involving paddle-shift-equipped cars, rather than a single issue affecting every use case in the same way.
Sebeco’s review also does not suggest that the issue is the result of one bad axle batch. The affected axle lot numbers span both 2024 and 2025 manufacturing dates, which gives us confidence that this is not simply a metallurgy issue isolated to one production run. Just as importantly, the current picture does not point clearly to any one supplier or component. The working conclusion continues to be that this is a system-level endurance application topic involving driveline geometry and shift strategy together. Additionally, we believe that the track characteristics experienced at Sonoma Raceway exacerbated the failures, given the continuous low/medium speed corners that require significant amounts of low gear/high torque shifts.
Accordingly, Sebeco’s development direction is mainly centered on three areas: driveline geometry through the gearbox spacer project, upgraded axles, and continued refinement of the paddle-shift strategy for endurance use. A major factor in that conclusion is that the only car at Sonoma that did not experience a driveshaft-related issue was running both the gearbox spacer package and a different ecu/paddle-shift strategy. Taken together, these three items currently represent the clearest path toward improving durability in this environment.
On the hardware side, the gearbox spacer kits move the transaxle rearward, which significantly reduces the CV deflection angle and subsequently reduces the stress on the outboard side of the axles. Shane Roberts of RMI — who is also an active NP01 endurance racer — has put significant time, resources, and energy into developing a gearbox spacer kit that is readily available and has already been tested through several endurance events. That package gives teams a direct route toward implementing the geometry update today. Teams interested in moving forward immediately can contact Shane at [email protected].
Sebeco is also developing its own gearbox spacer kit, which is expected to be available in approximately four weeks. This will provide teams with an additional in-house option for implementing the geometry update as we continue to support the platform moving forward.
On the controls side, Sebeco has now developed an updated gear shift strategy for cars running the paddle-shift system in combination with the Haltech ECU. That update is intended specifically for that configuration and reflects what we have learned through the post-Sonoma review. We believe that the current shift strategy, along with the Haltech ECU strategy are creating mis-timed downshifts which shock the transaxle and introduce torsion to the axles. The updated gear shift strategy aims to resolve these mis-timed downshifts. Cars not using the paddle-shift system, as well as paddle-shift-equipped cars running the AEM ECU, do not require an update at this time.
Additionally, Sebeco has upgraded axles that will be available beginning April 23, with an initial inventory of 20 axles in stock. These axles feature a process change in heat treatment of the axle and a slightly different design to improve their strength.. This gives teams another immediate path forward as we continue to improve and support the endurance application of the platform ahead of Barber and future events.
For teams that prefer not to move forward with the gearbox spacer project, upgraded axles, or adjust their paddle-shift strategy, Sebeco also continues to have the sequential shift package in stock and available as another path forward.
As with any change of this kind, validation remains a key part of the process. Sebeco’s goal is not simply to introduce updates, but to ensure those updates are properly tested and understood ahead of future race weekends. Sebeco has been actively testing on track each week over the past 4 weeks to validate the changes and continue its development.
Looking ahead, the next Zenith Racing Series event is at Barber Motorsports Park on April 25–26, where Sebeco currently has 11 confirmed entries. Between now and then, the company’s focus remains straightforward: communicate clearly, test thoroughly, and deliver practical solutions that improve confidence in the endurance application of the platform.
For further information on the updated paddle shift strategy, please visit the Sebeco forum and navigate to the technical bulletins section. Technical Bulleting TB001-2026 outlines the software download and installation instructions. For further information on the upgraded axles and gearbox spacer kit, please reach out to [email protected].