Not sure what exactly you are asking

can you mix fluid new and old? Yes
Can you drain the converter via drain plug? Yes

if I was doing it, I would drain the converter. It takes a few minutes of work. It will take time for it to drain.

 

Thanks for your feedback. My post about the C4 torque converter plug was whether or not there is one and how to find it.
After this post. I removed the inspection plate but, could not locate it on the converter.
Also, I ran the Ford id stamped codes on the tail shaft and discovered that my transmission has a C4 case but the tailshaft is from a C6 Shelby Boss.

Again, thanks,
T

 

couple new quarts of Type 4 that I have in the pan

Type 4 ATF would not be a good thing for that transmission. Verify the fluid spec for what you're putting in there.

 

Thank you for sharing your knowledge!
T

 

Thanks for your feedback! My bad on the reference to Type 4 fluid. I'm using Type F. Much appreciated, Thanks T

 

There is one and it's not hard to find.

 

If you have one it should be between two of the torque converter nuts, you may have to rotate the engine. I would do this with and socket wrench on the balancer bolt.

 

Thanks, I will look closer!
T

 

Some converters even have 2 plugs

 

The TC drain faces forward through a hole in the flexplate.

 

This is much appreciated. It helps to know what one is looking for. And where!
T

 

I never drained the TC

I change the fluid too often to worry about what's left in there
about every 5 years or 5k miles lol

 

My torque convertor and c4 trans drain whether I like it or not. So, after topping off, fluid is always fresh!

 

If it's leaking that means it has fluid in it. That's just efficient fluid level detection.