Heavy Duty Automatic Transmissions

Heavy Duty Automatic Transmissions

Automatic transmissions were first developed for the heavy Duty market in the 1970s by Allison and have steadily improved  over the years to the point where they are becoming more and more popular in heavy duty applications. Truck, Bus and other heavy vehicle operators are moving away from traditional heavy duty manual transmissions to the ease of self shifting automatics.

Automatic transmissions, traditionally were not as suited to heavy duty applications due to the torque converters loss of torque at low speed.  Higher engine power outputs have cured some of these problems. The complexity of changing gears hydraulically has been overcome somewhat by electronics and the introduction of AMTs (Automated Manual Transmisisons) into the market that still use a traditional type clutch but engage and disenagage automatically as well as changing gears automatically.

 

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Types of Heavy Duy Automatic Transmissions?

Some heavy duty automatic transmissions work the same way a light duty automatic transmission works. Basically, they are a bigger heavier item than those in smaller vehicles, designed to move much heavier loads more frequently. They use a torque converter to transmit power from the engine to the transmission and the shift points are now electronically controlled (instead of simple hydraulic pressure) and these electronics in the valve bodies are also reliant on the correct oil.

AMTs use a clutch driven system to transfer power from the engine to the gearbox and the gear changes are electronically controlled. They are two pedal systems with just accellerator and brake, so fit under the automatic transmission catagory.

DCT (Dual Clutch Transmissions) are now also available for heavy vehicles that offer the same benefits as an AMT with faster changes and no clutch to control.

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Heavy Duty Automatic Transmission Fluid

Heavy duty automatics use similar fluids to passenger car and light commercial vehicles. Many of the fluids are interchangeable as long as they meet the manufacturers specifications.

Common specifications for heavy duty automatics are -

  • Allison TES-295
  • Allison TES-468
  • Allison C4/C3
  • DEXRON® IIIH, IID and II
  • Ford MERCON®
  • Meredes Benz 236.91
  • ZF TE-ML 03M/04D/14C/16M/20C
  • MAN 339 Typ V1/Typ V2/Typ Z12/Typ Z3
  • Voith Turbo H55.633639
  • Volvo 97341