G or GTB

The Minneapolis-Moline
Prairie Gold “Letter” Tractors
“R” “Z” “U” and “G”
1936-1958

These highly collectible tractors were designed and produced after the formation of the Minneapolis-Moline Power Implement Company in 1929.

The Minneapolis-Moline Power Implement Company was formed by the merger of three old line farm machinery companies dating back to 1865. The Moline Plow Company, the Minneapolis Threshing Machine Company and the Minneapolis Steel and Machinery company were united by economic necessity. After the merger development was begun on the M-M line of tractors which became known as the prairie gold "letter" models “Z”, “R”, “U”, & “G.” After the 1929 merger these took several years to bring to market.

Explanation of Minneapolis-Moline’s “three letter” designation:

Officially, the prairie-gold and M-M cherry-red "letter" tractors were designated by three letters (example ZTU, ZTN, ZTS, & ZTI.) Often the first letter designated a model, the second letter a series, and the third letter a chassis and front end type. Colloquially we often refer to these tractors by the size letter such as a "Z" or "G" but the official designation included three letters.

Explanation of the First letter: (models such as RTI, ZTU, UBE, GTB)

The “R” model was the smallest and was designed to be a one/two-plow tractor. The "R" was first rated at 23.22 belt hp on gas. It was later re-rated at 27.09 belt hp.
The “Z” model was the next size and was designed as a two/three plow tractor. In 1937, the "Z" was rated at 26.84 belt hp on distillate. By 1950, the "Z" was rated at 36.20 belt hp on gas.
The “U” model was designed as a three/four plow tractor. In 1938, the UTS was rated at 36.48 belt hp on distillate and 42.88 belt hp on gas. In 1939, the UTU was rated at 42.71 belt hp on gas. In 1941, the U was rated at 46.87 belt hp on LPG. In 1954, the U was rated at 37.23 belt hp on tractor fuel. In 1954, the UB was rated at 48.38 belt hp on gas and 51.27 belt hp on LPG.
The “G” was a four/five plow tractor. In 1940 the GTA was rated at 56 belt hp. By 1955, the GB was rated at 74.95 belt hp on LPG.
In 1951 M-M purchased the BF Avery company and began selling the M-M models BF, BG, and V, which were principally one or two plow Avery tractors painted in the M-M prairie gold color and sold as M-M. Derivations of the BF were sold until 1955. These tractors are very popular with collectors. Their small size and lighter weight for “show-hauling” purposes is a plus. Explanation of the Second or “Series” letter:

ZT, ZA, ZB; RT; UT, UB, UB Special, GT, GTA, GTB, GTB-Diesel, GTC, GB, GB-Diesel

The second letter usually designated the series. Each subsequent series was improved mechanically, in horsepower, and in other options over its predecessor. The first series was the “T” series ("ZT", “RT”, "UT", and "GT".) "T" stood for Tractor. Subsequent series followed in alphabetical order and M-M endeavored to keep the series letters the same (or close to the same) for all of its models. The ZT became the ZA which became the ZB. The first Z series was the Visionlined ZT 1936-1948, the second “Z” series was the ZA 1949-1953, & the third was the ZB 1954-1955. In 1953, M-M elected to skip the “UA” series, so the “UT” became the UB. This was because the ZB was introduced in the same year that the second series of the “U” was introduced, and M-M didn't want to have a ZB and a UA in its line the same year. ZB and UB was more consistent for the same model year. In the “G” models from 1942 until 1954, a third letter was added to designate improved series. The “GT” (1940-42) became the GTA (1942-47) which became the GTB (1947-53) and the GTC (1951-53) followed by the GB (1955-59.)
Explanation of the Third letter: ZAU, ZAS, ZAN, ZAI, ZAE

The third letter usually designated a chassis and front end type. Type “U” is a universal, narrow front with two front tires. Type “N” is a narrow universal front with a single tire. Type “S” is a standard front with two wide non-adjustable front tires. Type “I” was an industrial standard front tractor. Type “E” is a wide front with extendible tire tread width from 56 to 84 inches at 4” intervals. Third letter M means Military, C means Cane, and O means Orchard.
Type N single front wheel tractors were useful for special row crops such as potatoes, however they were often converted to another front end type. This was done because the single wheel models were very hard to steer when the single wheel mired into soft soil. This conversion was often done by a dealer when the tractor was still new, so the first owner may never have known that it was originally a single front wheel model. Front end Type U (two narrow front wheels) was very popular, as it was the most versatile. They were taller, could steer between row crops, turn on a dime, as well as adequately do the heavy disking often relegated to standard front models. Serial number plates may not include all three letters. Actually, experience shows that all three letters typically appear on tractors during the early to late forties, but usually only the first or first and second letters are shown on tractors after that time. It is true, though, that some of the very early serial plates did not have all three letters either. For instance, early 1939 R's often have just RT stamped in the data plate regardless of the front end type. However, the later-model R's often have just "R" stamped in the data plate--no "T"