A few days ago, someone on these boards reminded me of a risk of doing a complete flush all at once: If the fluid is VERY old, then there could be a lot of gunk buildup in the transmission.
ATF contains detergents, but this detergent cleaning ability fades over time. Putting all new ATF in a gunky transmission could dislodge all that gunk too quickly, causing the clogging of certain parts of the trans.
If you want to be careful to avoid this risk, then BEFORE you do the full flush:
Remove one old quart of ATF, and replace with one new quart, then drive around for 100 miles. Then repeat once or twice more, or until you feel confident that you are not going to unleash a wave of gunk deposits. This is being seriously careful; use your judgement.
I would not worry about this problem at 30k or even at 60k miles, but at over 100k, consider it.
Thank you for this caution. I bought my '05 with the 5EAT at 115k on it. I have no record of any transmission service being done at all. I think I'm going to do a 4qt drain and fill a number of times. I drive 80 miles a day to work, so I'll probably do it weekly for like 4 times. to make sure I gently work out all the gunk.
DIY 5EAT ATF Flush
in Walkthroughs :: Basic Operation & Maintenance
Posted
Thank you for this caution. I bought my '05 with the 5EAT at 115k on it. I have no record of any transmission service being done at all. I think I'm going to do a 4qt drain and fill a number of times. I drive 80 miles a day to work, so I'll probably do it weekly for like 4 times. to make sure I gently work out all the gunk.