Piston Slap: The Importance of Servicing Your Car’s Transmission Fluid

Ron writes:

Sajeev,

Would the recall/lawsuit you previously mentioned be applicable to 2020 Malibus also? My girlfriend’s appears to have the same problem with hers.

Sajeev answers:

Sorry, no—the Malibu has a totally different transmission design. That episode of Piston Slap was about a transmission (for rear-wheel-drive vehicles) but this Malibu has a transaxle (for front-wheel-drive vehicles). Transmissions and transaxles can have interchangeable parts that can fail concurrently, but that’s unlikely. There could be a known issue with your transmission that has not risen to the level of a recall, but I didn’t see one on the internet. I recommend visiting the service department of a GM dealer to learn more about that, but I suspect your concern comes from worn-out transmission fluid in a four-year-old car.

I’m sticking with the transmission fluid as the problem here, but there’s another curveball coming our way: Malibus with the 1.5-liter engine came with a continuously variable transmission (CVT). These CVTs lack traditional gears in the gearbox, so here’s a quick visualization:

Okay, back to the issue of servicing your transmission fluid. The going theory on those GM transmissions from the previous Piston Slap is that the original fluid didn’t play well with moisture. That might apply to the Malibu, but remember all transmission fluid wears out over time. You could have accumulated a lot of miles in tough conditions since the vehicle rolled off the assembly line in 2020, and it may simply be time for a fluid-and-filter service.

There are times when changing transaxle fluid in a used car is a very bad idea, but this vehicle is too new to have that problem. (Hopefully.) When doing the service, make sure the shop uses the correct fluid. See the owner’s manual below:

CVTs always require a specific type of fluid, and putting in “traditional” automatic trans fluid will shorten the life of the transmission considerably. Sometimes there are tricks to remove as much of the old fluid as possible, and finding a shop that checks for this could be a good idea. But if you want to DIY this, there’s real value in doing transmission fluid changes in succession to flush out all the old fluid.

And at some point you also change the transmission filter, and this video suggests doing the filter change after the third oil change. Sounds fair, and we are lucky enough to see how to do this filter change in another video:

So do check with your dealer about any potential problems with your transmission, but I suspect this is a case of needing fresh transmission fluid. What say you, Hagerty Community?