My guess April 2019 for 657K
Brief bio from 1 lead engineer:
January 2015 – December 2016 2 years Managed project timelines, budgets, and resource allocation for New Product Introduction programs and maintained continuous improvement on 3-Wheel Tractor Scraper platforms. Lead 630K and 657K Tier IV emissions updates.
- Key contributor in the redesign of the 630K platform, which removed drum brakes and replaced with wet disc front and dry caliper rear, resulting in improved slope holding and braking performance, elimination of the maintenance costs associated with drum brake adjustments every 250 hours, and cost savings of $1K per machine.
- Drove research and development efforts serving as Tech Lead and managed team resources, created design concepts, and sourced supplier quotes for 657K program.
R.E. Monks run 631Ks; they've had rear axle housing failure on 1 machine, cracked about 4 inches (100mm) inside of the wheel.
C18 Tier4 with engine compression brake (Jake brake) to help prevent engine over speeds by automatically applying brakes and engine brakes via electronics. That is a PLUS, scraper engine over speeds have been historically the number engine failure cause, broken crankshafts and drop valves.
4 fatalities in 18 months; safety nazis are really enforcing brakes on scrapers.
631K proving ground to contractor testing