changing trans fluid to syn?

[deshemar]

I pick up today an 03 250 w/ v10. it has 119,000miles and i want to change tranny fluid to synthetic -has 4r100 tran- main question i have is do i try to get most of the old dyno fluid out? or do i just drop pan, change filter, and add new fluid? thanks for the help here.

[Mark Kovalsky]

You want to get all the trans fluid out. Just changing what's in the pan will change less than half.

The FAQs seem to be down right now, but go HERE and look under the '99 and up FAQ. There is an article there on how to change all the fluid. One thing that was left out is that you need to warm the trans up first.

Also, Ford has discontinued MERCON. You can still find it, but MERCON V has been changed to be compatible.

As for synthetics, I like Mobil 1 synthetic ATF.

[doczenith1]

I changed my fluid to Mobil 1 synthetic using the instructions in the FAQ that Mark mentioned in his post. It was very easy and did not take long at all.