Automatic transmission service

to flush or not to flush a transmission w/100k miles that functions very well?

Don’t “flush” the transmission unless the manual says to (do any?), but draining the fluid and changing the filter is always a good idea. The bit of wisdom that you should just leave an older transmission alone is a myth invented by mechanics who didn’t want to be blamed when a transmission dies from old age after servicing it.

“Service” according to the maintenance schedule that came with the car? Yes.

Flush? Maybe not.

Don’t flush; at that mileage, if the fluid has not been changed regularly, it will very likely cause problems.

As indicated, DRAIN the fluid and change the filter. Have this done by a reliable, independent transmission shop or a trusted mechanic. Don’t go to a tire store, brake shop or other chain to have this done.

Don’t flush; at that mileage, if the fluid has not been changed regularly, it will very likely cause problems.

I disagree. It is true that many transmissions fail shortly after having a flush or fluid change. However most transmissions at that age get their first fluid change because they are starting to have problems. They get the fluid changed (or flushed) and they blame it on the change, but in reality it is because there already was a problem because they had not been serviced until it started showing signs of problems.

The real problem is not doing the service until it was too late.

IF you are going to FLUSH at 100,000 miles without having done anything prior to the transmission, you should also drain the fluid and change the filter.

The flush will stir up all the loose stuf that has accumulated in the pan, and it could plug the fluid passages. Unless this stuff is removed and the filter replaced, flushing at that mileage will make the situation worse!

Reputable transmission shops will insist on draining the fluid and replacing the filter, if the car has a filter.

If this Towncar is from the late 2000’s, then the service manual does call for a complete fluid exchange (what many call a flush).

AAARRRHHHGGGGG!! Not again !

Yes, that “search” button up top is clearly meant for other people!