Synthetic trans fluid

[BadHabit]

If I switch to synthetic trans fluid, will it mix with the toyo fluid that will be left in the trans.? Does it have to be a complete, total fluid exchange?

 

[mikes4runner]

If I switch to synthetic trans fluid, will it mix with the toyo fluid that will be left in the trans.? Does it have to be a complete, total fluid exchange?

How many miles do you have on the truck and how often was the fluid changed?

I would drain and change the filter before putting any new tranny fluid in.

Mike