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Chad, the TA in the bigger tractors is nothing like the Super M-TA style, which is called the Mechanical TA. Anything with more than 70 horsepower built from '63-'85, from the 706 to the 3688, had the Hydraulic TA. Instead of using a planetary like the mechanical TA, the hydraulic TA was basically just two sets of constant mesh gears at the front of the speed transmission, one ratio for direct, and a lower ratio for TA. With the lever ahead, the Multiple Control Valve, or MCV, sends oil from the MCV pump to a hydraulic clutch pack, which locks the drive gear of the direct ratio gear set to the input shaft. When the lever is pulled back, the oil pressure is dumped from the hydraulic clutch pack, unlocking it. A sprague clutch, located between the drive gear of the lower ratio gear set and the input shaft instantly locks up. The MCV sends oil pressure to a hydraulic brake pack located between the sprague clutch and the input shaft, to keep the sprague clutch from freewheeling. There are many reasons why these TA's fail. Leakage in the MCV, TA, steering, lube, or brake circuts; abuse such as flying in off the road with a heavy load and shifting to TA to attempt to slow down will fry the brake pack. Water in the oil will flake the linings off of the clutch and brake disks. Leaving it in direct all of the time will cause flat spots to wear on the sprague clutch, which will then fail as soon as someone tries to use it. Misadjustment will cause hard shifting of the speed and range transmissions. As with any tractor, even the Super M-TA, the TA was always just an option. We have a 706 that came from the factory with no TA. There are many ways to eliminate the TA, ranging from taking off the handle and throwing it in the toolbox to installing a plain input shaft with just the direct ratio gearset, which is what the factory non-TA tractors have. The 361 was never used in a combine. The 407 was used in the very first 815's, DT-407 in the very first 915's. It is very hard to find these combines with these engines. If you are considering a combine engine repower, stay away from the 310 in the 715, unless you are good at making your own parts. At first glance, this engine makes perfect sense, since it is the little brother to the 358. However, the tractor flywheel will not bolt up to it's crankshaft.
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