XM376 (right) and XM377 (left)

It appears I missed a double-ended tank transporter when I was going over the LeTourneau- and Mack-built tank transporters last week, though this one’s somewhat different. Designated the XM376 (for the front unit) and XM377 (for the rear unit), each was an 8×8 rather than a 4×4, and both were designed to work together in one direction rather than with the ability to pull in either direction.

Crismon, who provided the information on this gigantor, was very critical of it. He noted that the entire unit weighed 64 tons, but was only designed to carry a 50-ton tank; that they were horribly non-maneuverable except in open fields; and that “the amount of money spent on this project must have been immense, and it served no practical purpose.”

We’re also not told who built this tank transporter. Both tractors used 560hp 1,195-cu.in. air-cooled Continental horizontally opposed eight-cylinder engines, backed by Allison four-speed automatic transmissions. Mack provided the axles (the two front axles on each unit steered), and the units were built in 1957. It’s likely the Army’s Detroit Arsenal assembled them, though I can’t yet confirm that supposition.

The transporter was designed to load tanks by uncoupling the rear unit, winching the tank onto the trailer, then recoupling the rear unit and driving off, at speeds of up to 35 MPH.

“The fascinating aspect of the double-ender story,” Crismon wrote, “is that for years prior to their advent, simple 6×6 tractors with normal semi-trailers had hauled tanks admirably, and they have done so consistently since the XM376/377.”

They were sold as surplus in 1961.