There’s no question that cars are getting more reliable and maintenance-free. You no longer have to clean carburetors, adjust timing, or perform frequent engine tune-ups the way older cars required. (Modern cars still require tune-ups, just not as often.) But as much as the average driver dreams of a maintenance-free car, it’s still a complicated machine that requires some upkeep. Maintaining your car includes everything from oil changes to major suspension and exhaust work. The manufacturer knows best when these jobs should be done — or does it?
In an effort to extend maintenance intervals and streamline maintenance schedules, many manufacturers have started to use sealed transmissions. As the name implies, a sealed transmission does not have a traditional dipstick for checking the fluid or an obvious way to add more. Contaminants can enter the transmission through such openings. A sealed transmission eliminates this path of contamination. It also makes it impossible, or at least quite difficult, for owners to check and maintain the fluid themselves.
Some manufacturers also claim that sealed transmissions contain “lifetime fluid” that doesn’t need to be changed. Many owners and professional mechanics don’t believe this claim. Even sealed transmissions require regular maintenance. While sealed transmissions do extend service intervals longer than older designs, they do not eliminate the need for fluid changes and routine maintenance.
The ZF 8HP and the BMW X5
A prime example of a popular sealed transmission is ZF’s 8HP. Introduced on the 2008 BMW 760Li, variants of it have appeared in everything from BMWs and Jaguars to Jeeps and Rams. This makes it a good example to compare maintenance interval recommendations from ZF and the auto manufacturers that use it.
There are many conflicting claims as to what ZF’s recommended maintenance schedule is for the 8HP. Some sources list it between 50,000 and 75,000 miles, but I could not corroborate this with the company. Instead, ZF offers a product data sheet for ZF LifeguardFluid 8, the fluid ZF specifies for use in the 8HP, that recommends a fluid change every 150,000 kilometers, or about 93,200 miles.
Let’s look at a modern BMW that uses the 8HP, the 2025 X5. BMW lists transmission fluid under the “Long-Term Rated Fluids and Oils” section on page four of its maintenance guide. BMW no longer uses the term “lifetime” fluid, as it did in the early 2020s. It now says, “Fluid replacement is only necessary when repairs are being performed,” implying that the fluid will last the life of the vehicle. What this really means is that it’s guaranteed to last the life of an extended power-train warranty. BMW offers extended warranties that stretch coverage up to seven years or 100,000 miles. It’s unlikely that a transmission will fail within 7,000 miles of ZF’s recommended maintenance interval, and then it’s no longer BMW’s problem.
A BMW spokesperson confirmed to Jalopnik that the automaker expects the original fluid to last the vehicle’s lifetime, assuming the owner didn’t want to follow ZF’s preventative-maintenance practice of a fluid change about every 93,000 miles. However, if the fluid in the 8HP is changed, the vehicle’s pan would also need to be replaced, as the pan and filter are integral.
The ZF 8HP and the Ram 1500
Far from the luxury and refinement of BMW, the ZF 8HP is also put to good use in the 2025 Ram 1500. Page 317 of the Ram 1500 owner’s manual states, “Under normal operating conditions, the fluid installed at the factory will provide satisfactory lubrication for the life of the vehicle. Routine fluid and filter changes are not required.” This directly contradicts ZF’s recommendation for regular, if infrequent, maintenance.
The 2025 Ram 1500 includes a five-year or 60,000-mile power-train warranty, well before the first transmission service that ZF recommends. Extended warranties covering the transmission are available for up to eight years or 125,000 miles. The chance of a transmission failure is rather low even at 37,000 miles beyond ZF’s recommended maintenance interval. Many owners will not choose an extended warranty this long, so it makes financial sense for Ram to roll the dice and simply cover repairs to what few transmissions may fail within the longest extended warranty.
A Ram spokesperson told Jalopnik that the transmission fluid would only need to be changed outside of “normal conditions,” such as in cases of “high trailer towing mileage and severity (heavy trailer, hot environment, climbing grades, etc.) and/or a significant amount of off-road usage in severe conditions, especially in sand and hot climates.”
We’ve picked on two examples here, but sealed transmissions in general do require regular maintenance, including fluid changes, regardless of what the vehicle manufacturer tells you. A well-maintained transmission can last 200,000 miles or more. Sealed transmissions make maintenance more difficult, particularly for the DIYer, but it is no less important than on any other transmission if you want to make it last. Don’t buy the hype of “lifetime” fluid, or the life of your transmission will be far shorter than it needs to be.
