Originally Posted By: Reddy45
I don't claim to be an expert on this but I've heard in the past that you should leave the fluid if you're beyond 150k miles without a change.
The reason? By that mileage, you're going to have worn down the friction material on some parts in the trans. You may not be anywhere near a rebuild, but replacing all the fluid means you'll actually have a lot less friction available. Slippage may occur as a result.
Not my words, but I saw it mentioned somewhere.
FWIW, I used to own an 02 F150 with the 4R70W and it started to slip on me around 145k miles. I was diligent about replenishing the fluid with Mercon V and a new filter every 60K. I sold the truck before I had to deal with any trans rebuilds.
You might look into adding some Lubegard Red as a preventative measure with that many miles. It has a good reputation as not just snake oil.
If transmission fluid is brown and/or smelled like it is burnt. CHANGE it!
Keeping track of OCI on the transmission is wayyyy cheaper than a transmission rebuild or a new tranny.
I just change my trucks fluid twice a year. Hot down here. And heat is terrible for transmissions.