My 100k mile 4runner trans. fluid smells sort of burnt, but when i smell the new trans. fluid out of the bottle it smells the SAME way. I know lots of people talk of not change burnt smell fluid but the new stuff smells that way to me. Mind you when i drained the pan the fluid was like chocolate milk, but nothing strange was in the pan, no bits or gunk. Just a little bit if very fine material on the magnets. I replace the 4 quarts that came out of the pan and am now debating if i will do that again tomorrow or flush the trans through the cooling line, or do nothing. It shifts as good as ANY new car I have been in so who knows.

 

You'd know if it was really burnt, smells bad....I'd do a few pan drain and refills (maybe drive for 500mi between each) until it was a nice red color again on the dipstick. I don't think a flush would be an issue either if you wanted to go that route as well.

 

Drive it for awhile, 500 miles or another 1000, then do the pan again. Its a little safer to introduce new fluid slowly into the system if you have a fear of it being burnt.

Just to note, my fluid looked great when I checked it via the dipstick, but when I drained it from the pan it was much darker. So I let the darker stuff sit in the catch pan for awhile and when I rechecked it all of the dark stuff was settled at the bottom and the sorounding fluid was cherry red. No burnt smell.

What fluid are you switching to?

 

I am using the valvoline Maxlife for now. Once most of the old fluid is replaced with new I plan on going with a synthetic upon the next round of fluid changes. Just my instincts here, but i dont want to introduce anything too different right away.