See sticky here:
https://carkiller.com/scottykilmer/qa/atf/
Check the fluid - how does it look? If relatively clean, I would drain and fill only (not flush) the fluid and also change filter. Keep the old fluid in case there are issues afterwards.
You don’t want to flush a transmission because it can potentially cause some damage. High pressure chemical fluid is pushed through the transmission backwards and it can dislodge some particles that allows the transmission to shift smoothly - this is especially true on older/higher mileage cars. Doing a simple drain and fill is a good idea for routine maintenance to keep fresh fluid in the transmission. It makes sure the correct viscosity and flow of the fluid is maintained, which is what the transmission was designed for.
which shop does this? (push high pressure chemical through the transmission)
My Toyota dealer told me a pressurized chemical flush is put through the transmission to clean it out when I inquired about a transmission fluid maintenance. (obviously I did not get it done)
It sounds like a lot of nonsense. The chemicals would get trapped in the tranny.
Exactly! One of the many reasons I no longer take my Toyota to the dealer.
Never Flush.
Do Drain and Fill at recommended intervals. This is also known as a fluid exchange.
Never Flush.
what about this Ttech fluid exhange?
Apparently some Fords you can’t drain and fill; they need the fluid pumped out which is what that machine is doing. But it’s also not using high pressure to displace it - to be clear.
My point is, don't get too hung up on the nomenclature. Different people will have different names for the same thing.
The main reason, is because you don't need to. The insignificant benefit of squeezing out every last drop isn't worth the risk of molesting your vehicle like that, and popping a cooler line later or something. The concept of minimally invasive surgery applies to cars as well as to people.
That being said, I don't think using a fluid exchange machine on a healthy transmission is "dangerous". I have flushed all of my vehicles (including DIY), and the transmissions shifted perfectly.
Some Fords don't have transmission pans, so you flushing them is the only to exchange the fluid.
And in that case you are really just using the transmission’s own pump to move the fluid which happens during normal driving - if transmission could not handle that pressure we’d really be in trouble.
Right. And it's possible there's machines out there that do use high pressure. It's safer to just say no to it. It's usually offered to pump your wallet, not make your car run better anyway.