Rapha

Hey folks I got a new to me 2007 base model SWB RWD and ML. The car was very dirty and neglected when I got it but mostly just dirty inside and out, that I was able to clean and polish and it looks great now,
I am trying to get the maintenance up to speed, everything works great and transmission shifts beautifully smooth. I am thinking of taking it to a transmission shop for oil and filter change, the car has 155k miles or 250k km, I'm in Ontario-Canada. I'm a bit unsure if that's a good move or not, I have no history of the car's maintenance and transmission might had never been touched, any thought?

napamikey

On my 12 460l AWD it had a change at 120k miles (dealer) and 250k miles (drain and refill) no issues. Just make sure it is filled correctly. After last change was acting wonky and went into safe mode multiple times intermittently. Turned out was down about a half quart and has been flawless for last 30k miles, now at 280.

Gerf

At that mileage if it's still operating without any issues I would just leave well enough alone, drive it for awhile and see if anything else comes up.

Marc780

I'd want to change the ATF too at your mileage and I'd have the same concerns. I think you'll be just fine changing the fluid, even so I think I'd start with a simple fluid change as NapaMikey says (with no flushing and no attempt to replace all the fluid, at least this time). Then drive it for a while to see how the car responds.
If it responds well (as expected) I'd do another drain and refill later, say in 6 months or a year, and just replace the fluid gradually.