Beyond Repair: KIRKS Remanufactures Allison Hybrid Stators to OEM Standards
Like our hearts are vital to keep us moving, the Allison Hybrid H40EP and H50EP Drive Unit Stators are vital to performance. When these fail, the ripple effects can stall entire schedules. The stator is a critical component of something much bigger, and they need more than industrial “CPR.”
We’ve engineered a process to remanufacture the Allison Hybrid H40EP and H50EP stators with expertise, precision, and rigorous in-process and final testing. We revive failed stators, restoring them to OEM standards so they return strong, safe, and ready to run.
These critical hybrid bus components can be brought back to life with reliable performance and with cost savings that respect your budget. We preserve the integrity of the original lamination stack and repair it as necessary before rewinding so that it performs as new.
Our remanufacturing process ensures every stator meets OEM specifications for performance and safety and gets them to your shop with significant cost savings.
The Hybrid Stator’s Job Description: An Overview
Power Generation: Hybrid stators are responsible for generating electrical power. When integrated with the bus’s electric motor, they convert mechanical energy into electrical energy, enabling the vehicle to operate in electric mode.
Energy Recuperation: During braking, hybrid stators can facilitate regenerative braking. This function captures kinetic energy that would otherwise be lost and converts it back into stored electrical energy, enhancing energy efficiency.
Operating in Multiple Modes: Hybrid stators support various operation modes, allowing the bus to run on electric power, traditional internal combustion engines, or a combination of both. This versatility helps optimize fuel consumption and emissions based on driving conditions.
Smooth Power Delivery: Hybrid stators provide a smooth and responsive power delivery, enhancing the driveability of the bus. This ensures consistent acceleration, resulting in a better passenger experience.
Control Integration: The stators work in conjunction with the bus’s energy management system to optimize the use of power sources. This includes deciding when to draw power from the battery or the engine based on real-time needs.
Here’s a Quick Overview of Our Proven Remanufacturing Process
To confidently offer Allison Hybrid H40 EP and H50 EP Drive Unit Stator replacements, KIRKS needed to learn its nuances and build a process around its quirks and tolerances.
- Receive the failed stator or housing assembly
- Burn off original varnish and insulation
- Strip copper windings and inspect the lamination stack
- Clean and repair the core
- Add new insulation and rewind with precision-fit magnet wire
- Install new RTDs
- Run pre-varnish electrical testing
- Varnish and bake the unit
- Reinstall stators into housing (if applicable)
- Crimp on lugs (for units sent and replaced in the housing)
- Run final electrical tests and quality checks
- Package and Ship
KIRKS Allison Hybrid Stator Remanufacturing Process, In Detail
- We Welcome One Stator or Both Stators in the Housing
Transit teams can send us a single failed stator or both stators that are still installed in the drive unit housing. Often, these units arrive coated in oil and dirt with electrical failure points: a short, a burnout, or some combination of both.
If your team isn’t equipped to remove stators from the housing (which requires extreme control and precision), we’ll take care of that too, from disassembly to return-ready installation. - Burn, Strip, and Preserve
We start by placing the stator in a burn-off oven to remove the original varnish. Then we remove all copper and insulation, taking care not to damage the lamination stack.
Only the lamination stack is reused. The lamination stack is engineered with hundreds of thin steel laminations. These layers are critical to magnetic performance, so cleaning, inspection, and restoration of the core is vital.
- Clean, Insulate, and Rewind the Stator
Our team hand-wraps each coil, laying down fresh insulation to prevent contact between copper and core. The placement of these windings is not just about neatness; it’s a matter of millimeters. If copper is positioned incorrectly, it can rub against the housing or rotor, leading to internal shorts or full system failure. In this way, building a stator is like fitting a racecar engine: performance comes down to precision, and small errors can lead to major consequences.
After winding, we tape and tie the coils securely. At this point, the stator is ready for its first round of tests before it’s varnished & baked.
Summary of rebuilding the stator:
- Apply new insulation
- Rewind and position the copper wire
- Hand-wrap new copper windings with polyester tapes
- Crimp and position each coil with millimeter-level accuracy
A precise gap between the lamination and housing ensures no copper comes into contact with the housing. This is a must for preventing internal shorts and failures.
- Pre-Varnish Electrical Testing
Every stator we rebuild goes through a six-point electrical test protocol based on Allison’s OEM specifications. This isn’t just a checkbox process.
Each test tells us something specific about the performance and safety of the unit:
- Resistance Test – Confirms that all coils are balanced and properly wound.
- Surge Test – Applies high voltage to check insulation strength between coils.
- Insulation Resistance Test – Measures resistance between windings and the stator core to prevent shorts.
- Hi-Pot Test (High Potential) – Injects 2,210 volts to ensure the insulation can handle real-world load without leakage.
- RTD Testing – Verifies that both built-in thermal sensors (RTDs) are functional and accurate. There are two: it’s redundant with a secondary one.
- Final QA Pass – The unit is tested again, either as a standalone part or fully installed in the transmission, before shipment.
We run these tests on proprietary equipment with pass/fail indicators and detailed waveform output. We’ll even snap a photo of the readouts for your records, so your team knows exactly what went into the certification.
Think of this as a medical checkup; we’re not just looking for signs of life; we’re making sure this stator is healthy enough to go the distance.
- Varnish, Bake, and Lock It In
Once the stator passes testing, it’s dipped in high-performance varnish and baked again. This hardens the shell, sealing in the coils to prevent vibration breakdown and environmental damage.
Important: Once baked, the unit can’t be modified, so everything must be perfect before this step. That’s why we test both before and after varnishing.
- Final Assembly and QA
- Crimp the power lugs (if we’re installing it in the customer’s stator housing)
- Perform a final QA test, either standalone or inside the dual-stator housing
KIRKS Reman Means Ready, Reliable, and Real Savings. What You Get:
- Remanufactured Allison Hybrid H 40 EP and H 50 EP Drive Unit Stator Replacements built to OEM performance specs
- Full electrical test documentation
- Reinstallation into housing (optional)
- Expedient turnaround, reliable support, and proven performance
- Reliable replacements at a fraction of buying new
The State of Stators, Remanufactured with KIRKS’ Approved Equal SealTM
The KIRKS’ mission is to keep people moving, which means we’re helping you keep buses running, routes on schedule, and fleets out of downtime. Every remanufactured Allison Hybrid Stator Drive Unit from KIRKS comes with our Approved Equal SealTM, delivering quality, reliability, and peace of mind.