1955 Minneapolis-Moline UBD Special

Special thanks to Brian Gonyea

The last years of corporate independence for Minneapolis-Moline were not filled with a stagnant model line. Despite financial upheaval, and having to fight tooth and nail against larger companies in the ag market, from the mid-1950s to the corporate acquisition by White Motors in 1963, Minneapolis-Moline (M-M) fielded a solid line of tractors. One of them was the U-Series that began in 1938 and ran to 1957.

Ansel Price’s 1955 UB Special diesel is the 292nd of it’s kind and was barely in the 1955 production range. It mounts an adjustable wide front and is equipped with power steering. This unit was restored by Mt. Hope Tractor in Millersburg, Ohio, and was a nut and bolt job.

Slow to Diesel

M-M was slow warming up to diesels. M-M was very big into LPG-fueled engines because in their most lucrative market, the wheat belt of the upper Midwest, LPG was very popular. Still, diesel power was inevitable and the first volume production M-M diesels came as an option in the 1954 UB line. The UB had debuted in 1952 as an evolution of the original U-Series. Most of them were gas or LPG powered but a very short run of under 20 diesel powered tractors were built then, likely to test the market. The new engine was a diesel adaptation of their big 283 cubic inch gas four. Because M-M had purchased a license for Lanova Power Cell system, known for it’s slow and gentle combustion, that meant a lower end design could be shared between gasoline, LPG and diesel. The UB diesel line was built in ’54 and into ’55, but an improved model, the UB Special, debuted in ’55 and ran until ’57.

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From the rear, you can see only a swinging drawbar and PTO. The UB Specials were not offered with a 3-point hitch. Historically, M-M offered mostly wheatland or universal tractors because customer demand was not great for the rowcrop types with 3-point hitches. The platform configuration of the UB line did not lend itself to a 3-point because the tractor was mounted from the rear. That would change, of course and the more of the tractors M-M built in this size after the UB Special had three point hitches. Aftermarket 3-point hitch kit available for the UB and UB Specials.

The Special

What was special about the Special? Mainly the availability of optional power steering and the changes in the front end options that came with it. The brakes were updated from drums to discs and a few other improvements also came for the Special. The new front axle bolster necessitated some styling changes, the updated tin giving the Special tractor a more angular and modern look.

The D238-C4 was a big, slow turning four-cylinder that made a lot of torque. Displacing 283 cubic inches from a 4.25 x 5.00-inch bore and stroke, the crankshaft was supported by three large main bearings and the lower end was very similar to the M-M gas engines. The cylinders were cast in pairs and were parent bore, which was M-M SOP. The cylinder heads, again cast to cover two cylinders, contained the diesel combustion chamber and Lanova cells. Note the Lanova cells screwed into the head below the exhaust manifold. The diesel heads used twelve bolts versus only seven for the gassers. The pistons had two oil control rings versus just one for the gas engines. The D283-4 were offered in power units and rated for 49 horsepower at 1300 rpm on the flywheel. It was fuel efficient, as most Lanova diesels tend to be. We have not found a torque spec, but calculated torque at 1300 rpm is 268 lbs ft. so between the estimated peak at 800 to 1000 rpm, the number is likely nearer 300 lbs-ft. A Bosch PSB-4A injection pump was used.

In 1955, both gasoline and diesel UB Specials were built, but for ‘56 and ‘57, only diesels were made. The powertrain remained largely the same as the previous UB, with a 5-speed manual gearbox behind the diesel. Prior to the Special, the UB tractors were different enough to each get a different designation. The UBU had a double-wheel narrow front, the UBN had a single front wheel and the UBE had a wide adjustable-width front axle. With the Special, all the axles could work with the same new front bolster and power steering system so the separate designations were not used. Still, the power steering was an option, so not all Specials had it. The heavy, arched axle used on the similar UTS series wheatland models wasn’t an option for the UB Special, but for ‘55 and ‘56, the UTS had enough of the updates to be a defacto wheatland “Special.”

The operator’s station was typical mid-1950s. The “iron butt” seat was backless but a seat pad was a necessary accessory for most human’s anatomy. The UB Special had a nice suspended seat going for it, though and, the high platform position offered good visibility.

Special Diesel Power

The four-cylinder UB Specials were at the heavy end of the middleweight tractor class, so needed a big, powerful engine… even if it was a four. The D283-4 engine was modular in a sense, sharing many parts with the 6-cylinder D425-6 series engines used in the GT and GB lines. There was no Nebraska Tractor Test done on the UB Specials, nor the UB diesels, so all we have are the factory ratings. M-M-rated the UB diesel with 40 drawbar hp and 45 hp on the belt. The UB Special diesels had some updates versus the UB, but they didn’t add any power.

Life and Times

The UB Special diesel was a short-lived and relatively low production model. From ‘55 into ‘57, just 520 were built making them a relatively rare find today. With interchangeable front axles, their configurations run the gamut, but the adjustable wide front axle appears to be the most common survivor. The UB Special diesel was replaced in the lineup by the very much updated 5-Star diesel starting in 1957.

A cross section of the M-M engine. Both the 425 cubic inch six and 283 cubic inch four shared identical architecture and shared many parts. Starting with the 5-Star, the D283 became the D336 with a bore increase from 4.25 to 4.625 inches, bringing the engine close to being square. With other tweaking, that was enough to bring the D336 PTO power up 10 ponies to 55 horsepower at 1450 rpm.

SPECIFICATIONS

1955 Minneapolis-Moline UBD Special

Engine:D283-C4, four-cylinder diesel, Lanova Cell
Displacement: 283.7 ci
Bore & Stroke: 4.25×5.00 in.
*Rated PTO Power: 45 hp @ 1300 rpm
*Rated Drawbar Power: 40 hp @ 1300 rpm
Compression Ratio: 15:1
Transmission: 5-speed (5×1)
Weight: 5,550 lbs (narrow front)
Maximum Ballasted Weight: 8,700 lbs
Tires: 6.00-16 front (others optional)
12-38 rear (others optional)
*Fuel Capacity: 21 gal.
*Top Speed: 15.6 mph
* As Rated by Minneapolis Moline

SOURCES

Mayer Farm Equipment
www.mayerfarmequipment.com
740-426-6307

Mt. Hope Tractor Restoration
www.mthopetractor.com
330-674-3637

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