Transmission fluid change

BRUSCIAJ

MEMBER
2003 TOYOTA HIGHLANDER
3.0L
6 CYL
2WD
255,000 MILES

Hi, just watched your video on doing the transmission fluid change on the Toyota highlander, fantastic videos super in depth. My question is, I've had the car for a long time and quite a bit of miles; I was told that doing a fluid change would be a bad idea because all of the gunk is helping to lubricate it, but as of recently it's starting to shift pretty rough. In your opinion, would I be better trying to change the fluid, or should I give up on the car and wait until it gives out? It's currently my daily driver.

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,164 POSTS

Hi,

The theory is based on how dirty the transmission fluid is. If it is extremely contaminated, new fluid will flush it out and become dirty itself very quickly. This can lead to it slipping. Simply, you have removed a portion of the debris that was helping with friction between the clutch plates. The new fluid does have a detergent in it, so it will start cleaning.

However, in most cases, it doesn't cause this to happen. If it is shifting hard, chances are there is a restriction in the filter or transmission causing the line pressure to lower. That can eventually lead to the clutches failing.

How dirty is the fluid in it presently? If you were to describe its color, what would it be, black, red, or dark red? Was the fluid ever changed in the past?

Let me know.

Joe