Light Duty Gets Tough

Ten years ago, makers of light-duty commercial vehicles were making great strides in engine technology, but their automatic transmissions were another story. Problems began in model years 1989 and 1990, when electronic controls were introduced by market leaders Ford Motor Co. and General Motors Corp. GM’s 4L80-E and Ford’s E4OD-four-speed-overdrive automatic transmissions-typically burned out at 60,000 miles and sometimes less. Earlier Turbo Hydra-matics and C6s often lasted more than 100,000 miles.

The Maintenance Council of the American Trucking Associations-comprised of suppliers and fleet maintenance managers-set up a study group called S.14 to examine the problem, and last summer the group presented a recommended practice on light-duty automatics. It includes technical information from manufacturers and suppliers of fluids and other products, and focuses on how to extend lives of transmissions.

Discussions of failures revealed that mechanics were ignorant of the newer products’ maintenance needs. While their electronic controls resulted in good drivability and helped engines’ fuel economy, few mechanics knew how to work on them. Also, complex circuitry in modern light trucks was tied into that of the automatics; the transmissions were no longer stand-alone components, but mechanics didn’t realize it.

Rebuilders reported they encountered many units that were returned as “failed” but had no apparent faults. They pointed out during TMC sessions that mechanics had to learn how to properly diagnose problems using the correct procedures and tools. Manufacturers must get these materials, along with training, to fleet and dealer shops.

Included in the RP is a section on aftermarket filters because some S.14 members concluded that a good externally mounted in-line fluid filter solves many problems. The standard filter supplied by original equipment manufacturers has always been a fine screen mounted inside the oil pan, the draft RP notes. Fleet testing of a magnetic filter sold by a Detroit-based rebuilder shows the device extracts ferrous metal particles that would otherwise destroy internal parts, as well as nonferrous contaminants. The Magnafine filter is easily installed in the cooler line. It is made by Boss of Australia and sold for about $18 US retail by National Fleet Service of Detroit (1-888-468-7933). Meanwhile, GM and Ford engineers have worked feverishly to find their products’ problems and correct them. Ford, for instance, brought in thousands of “failed” transmissions, tore them down, and analyzed them. Many were found to be free of defects, but many more needed changes. Programs of “continuous improvement” have also toughened GM units.

Ford’s result is the new 4R100, which is going in the SuperDuty F Series just unveiled. It uses 60% new parts compared to the E4OD, according to one source. The updated 4L80-E set for GM’s ’99 model C/K trucks is far different than earlier units.

Cooling is also an important consideration. Coolers are standard on automatics in most class-2 through -4 vehicles, industry sources say. Where the coolers are mounted seems as important as having them in the first place. If air flow to the heat exchanger is stilted, fluid temperature will not be reduced enough. Isuzu claims it has seen few complaints of failures in its gasoline-engine NPR, which uses GM’s 4L80-E. The reason, engineers think, is that the cooler is mounted at the front of the flat-faced low cabover and easily catches cooling ram air. On conventional-cab pickup or short-nose van-type chassis, air flow to the transmission cooler seems less effective.