mph. The model experienced poor sales due to its high cost of US$2,155 (1938) (double that of a Farmall or Deere),. A general recession starting in 1938 also negatively impacted sales of this and most other durable goods. Only 125 of the UDLX were produced before production stopped in 1941. UDLX was part of one of Minneapolis-Moline's most popular series. The U series saw a number of variants, including the UTU, UTS, UTL, UDU, UDU, UOPL, UB, UTIL, and UT. GT Introduced in 1941 this tractor was powered by a four cylinder petrol/paraffin engine which produced 40 hp and which was sufficient to give it a five-plow US power rating. Its transmission had four-forward and one-reverse gears. Uni-Tractor In the early 1950s M-M introduced the Uni-Tractor which was a three-wheeled powered unit used to drive other units. The concept was instead of having different tractors and harvesters, one power unit mated to the correct unit could do all the jobs a farmer needed—i.e. of as M-M sales stated "All-in-One". While it was sold in small numbers the concept never was popular with most farmers. Many farmers referred to the Uni-Tractor as the Minneapolis-Moline Motorcycle. The Uni-System design was sold to New-Idea in 1963 after being acquired by White. ZB series Introduced in 1953 the ZB was an improved version of the ZA tractor with a more comfortable seat and improved steering. It was powered by a four-cylinder petrol engine which produced 34.8 hp and drove a gearbox with five-forward and one reverse gears. The ZBU version had a tricycle front axle with double front wheels, while the ZBN version had a single front wheel and the ZBE had a wide front axle. production stopped in 1955. M series The M series was introduced in 1960 with the M-5, followed by the M-504 in 1962, the M-602 and M-604 (4WD) in 1963, and finally the M-670 in 1964. The M series ended production in 1970. G series The six cylinder G series actually started in 1954 when Moline took the engine block of their six cylinder gas power plant engine turned it into a diesel and installed it on a G series tractor in place of the four cylinder. In 1955 they made a few changes to larger engine bearings and the final drive and introduced the model GB Diesel. The six-cylinder G series comprises the largest and most powerful Minneapolis-Moline