Medium Duty: Transmission and PTO Upkeep

Maintaining transmissions and PTOs is serious business.

Warren says Eaton’s UltraShift HV transmissions are compatible with all major PTO suppliers, and require no servicing other than routine inspections to ensure the bolts are properly secured.

“From the factory, it is going to come with synthetic lubricant, so there’s no need to touch this transmission, there’s no filters required and there’s no lubricant changes required,” she says. “It’s just drive and go.”

A relatively new addition to the medium-duty market is Eaton’s hybrid transmission, with its engine-off PTO function, which means a user or driver can run the PTO without having the engine on, saving fuel, noise and emissions.

“The desire for utility companies is to be able to not have their engine running the entire time they’re at the job site,” Warren says. “With this ePTO feature, it allows the operator to turn the vehicle off and run the PTO, just using an electric motor powered by the batteries with the hybrid system, so that’s definitely a value add.”


Staying on top of fluid and filter change intervals is critical, says Duner, particularly in automatics.

“In an automatic transmission, fluid does much more than just cool—it lubricates, it transmits power, it applies clutches, it carries dirt away—so utilization of the correct fluid for the vocational type and the product is equally important because of the wide variety of transmission applications we support,” he says. “We look at mileage or hours, whichever comes first. These are commercial vehicles; they are designed to do one thing—make money for somebody, and they can’t do that if they’re broken down. It’s all about uptime.”

Many technicians assume transmission problems are electrical-related, Duner says, but first investigating the cause of trouble can save time and money.

“Look at fluid levels, look at installation items, rub-throughs on wire harnesses, chafing on hydraulic hoses, look at the integrity of the vehicle cooling system,” he says. “Automatic transmissions generate heat, they share the cooling system with the engine; we want to keep the coolant on the right side of the oil cooler and the transmission fluid on the other side of the oil cooler—the two shouldn’t mix.”

If there’s an indication of a failure there, it can bring glycol contamination into the transmission, Duner says, which will shorten the life of the clutch disks within the transmission. Conversely, if you get oil in the water side of the cooling system, then the overall efficiency of the cooler diminishes accordingly.

“Do the basic walk-around on a vehicle,” he says. “Transmissions should not leak, so if there is a leak, it should be addressed with some speed. Any issue of severity will turn on an indication to the consumer that there is a problem—that could be as simple as a check transmission light or it could be as severe as a fail in range response to a significant failure, that says, ‘Something bad is going on, I’m going to stay in the range I’m in, not allow upshift or downshift until the operator pulls off to the side of the road and seeks council in getting that repaired.’ So there are severity indicators relative to the output of the electronic control system as it self-monitors its condition.”


While transmissions are generally trouble-free, Johnson says, automatics present greater challenges for technicians.

“Filtration is extremely critical on those,” he says. “I would definitely recommend a regular program for servicing automatic transmissions, changing fluid and filters, making sure the coolers are operating properly; that they’re clean enough.”

Heat is the biggest enemy of automatics, Johnson says, which makes proper cooling all the more important.

“There are number of things that can cause an automatic transmission to overheat—the cooling radiator is clogged up or damaged and you’re not getting adequate cooling fluid—both low and high fluid levels will cause problems,” he says. “If you put too much in, you’ll get foaming, which causes a number of problems. It’s critical to maintain the proper level of fluid, and make sure you know what the process for checking it is for that particular transmission.”

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