A heavy-haul diesel locomotive from GE's Universal Series, easily identified by its thick, blocky carbody and distinctive chugging exhaust sound. Crews gave them this naval nickname because of their utilitarian shape and tendency to leak oil or wallow heavily on rough track. Though largely retired from mainline service, their design set the template for subsequent high-horsepower freight engines.
Heard on the job
We caught an old U-boat on the local run and the cab rattled so hard my teeth hurt.
Insider tip
You can usually spot an old U-boat by the thick radiator wings at the rear and the slow, heavy throb of its four-stroke prime mover.