years ago:
my brother needed a car right away as he lost a 2002 VW diesel in a wreck. working on 230,000 miles going towards a million)
I bought a 2003 saturn 300 from a neighbor. I asked him if he ever changed the trans fluid in 10 years / 150,000 miles of urban stop and go driving. ..
the answer was no. "the manual says it does not need to be changed"
and there is no dipstick to check. ...
still running fine though. I looked what fluid was in it: plain old Dexron III dino fluid, (non-synthetic)...that in a truck would be replaced every 30,000-40,000 miles....or more often in stop/ go driving; towing, on mountains/ snow/ dusty. (you know like "anywhere", any vehicle gets used)
(so a 2003 saturn,.... a sign of dipstick-less things to come)
I had my brother call 5 trans shops and ask for a pump through, and not just a drain / fill. (and they said the existing was dark brown, ...no coffee grounds though...so not actually breaking down and clogging the works up yet).
$300 later, and he drove it for 4 more years, no leaks no troubles.
until the rear subframe thing rusted through and the car's ass landed on the blacktop while parked. (and he had a junk man haul it away, ... ...a sad end to many a Chevy malibu type).
at least the GMC company pr;cks did not just put a 100% sealed transmission in for it to die in 100,000 miles exactly.