Full-track Prime Mover M34.
The M34 was a tank recovery vehicle M32B1 that had its winch, armament, crane, and other recovery-specific stowage removed. This was used instead as a tractor for the towed 8" gun and 240mm howitzer until the 38-ton high-speed tractor M6 could be fielded. (Picture from Catalogue of Standard Ordnance Items, second edition 1944, volume I: Tank and Automotive.)
