Each bus was stripped to its chassis, some of which were almost four decades old. The diesel engines, exhaust systems, fuel tanks and old transmissions came out. The new components went in:
- DANA TM4 SUMO HP electric motors (145 kW, 625 Nm)
- Allison T280R six-speed automatic transmissions
- Six lithium iron phosphate battery packs (240 kWh total)
The Allison T280R, originally developed for diesel buses and adapted for electric use, delivered exceptional benefits. Its Continuous Power Technology smoothly multiplies torque, eliminating the jerky shifts passengers feel with other systems—particularly noticeable on the upper deck. Willms deliberately opted for a transmission-equipped system rather than gearless direct drive. "We selected a drive system that has already proven itself in municipal vehicles, such as refuse collection vehicles," he said. |
The Results: Lower Costs and Improved Passenger Experience
Following the retrofit, Willms Touristik experienced these results:
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"The acceleration is smooth, the maneuverability is excellent and there are no jolts when shifting gears. I also anticipate that the electric drive will eliminate wear and tear and high maintenance costs."
- Sacha Willms, Owner of Willms Touristik
By retrofitting rather than replacing, Willms saved resources and keept functional buses in service. The open-top CityTour buses now run almost silently through Cologne's streets, demonstrating that retrofitting can be both economically and operationally sound—particularly when paired with proven technology like Allison's automatic transmissions.