Toyota's new four-speed automatic transmission, the A40D, features 0. 689:1 overdrive for improved fuel economy and reduced engine noise. This is brought about by fitting an added planetary gear set between torque converter and conventional three-speed automatic. Clutches in the overdrive serve two purposes: they handle engagement and disengagement during 3-OD and OD-3 shifts, and they also work selectively to smooth shifting of the conventional unit. The transmission has a dash-mounted overdrive lockout as well, to preclude any hunting sensation in certain vehicle modes. In general, there is an across-the-board decrease of 2 dBA in interior noise traceable to reduced engine speeds. With regard to fuel economy, the overdrive transmission improved EPA city figures by some 2.5% and highway values by almost 21%.

Media Info

  • Pagination: p. 56-59
  • Serial:
    • Automotive Engineering
    • Volume: 86
    • Issue Number: 7
    • Publisher: Society of Automotive Engineers (SAE)
    • ISSN: 0098-2571

Subject/Index Terms

Filing Info

  • Accession Number: 00183267
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Files: TRIS
  • Created Date: Dec 29 1978 12:00AM