Can auto trans fluid be mixed?

[sr17]

Apologize for the rather ignorant qestion, but I just don't know much about transmission fluid.

I just bought a Mityvac fluid extractor and figure it could be good to try and use to "freshen up" the fluid in the transmission on my Astro van.

Problem is I have no clue what is in there now - all I know is a) the fluid is about 18 months old b) the stuff is red, and c) it is over filled.

If it is safe to mix fluids, what is a good fluid to put in?

 

[Pablo]

If you put any flavor of Dexron in there, no harm will come of it.

 

[45ACP]

Yes you can. Of the same "type."

Some people put one or two quarts Mobil 1 ATF (its purple, synthetic) and the rest the normal transmission fluid when refilling an ATF. "No pull" is always the fear. It rarely happens.

Did you line flush, drop pan, or are gonna Mityvac it? Be sure to Mityvac it hot and have ALL the transmission fluid ready to put back in.

I have also heard that some people put one quart Type F fluid in with whatever fluid, to raise pressure in the trans and make it shift "firmer" but that is wholly unconfirmed, a "racer's trick" ?

 

[dwendt44]

Astro vans, like all GM made stuff, has an actual filter in the transmission pan. Pump out or line off change doesn't do any good to the filter or the fines in the bottom of the pan.
Most especially true of the first fluid change.

 

[eagle23]

If you have the ability, use the Mityvac to drain most of the pan, then drop the pan and change the filter. Dropping the pan filled with fluid is usually the worst part.

Once that's done, you can Mityvac every 20-25k if you want. I'd use it like Honda's 3x drain/refill: drain the pain with the Mityvac, refill fresh the 2-3 quarts you just removed, drive around the block and do it again, 2 more times. You will have replaced >80%, closer to 90%, of the old stuff with new, and your transmission will be happy

 

[sr17]

Originally Posted By: dwendt44
Astro vans, like all GM made stuff, has an actual filter in the transmission pan. Pump out or line off change doesn't do any good to the filter or the fines in the bottom of the pan.
Most especially true of the first fluid change.


The current fluid and filet have around 10K miles on them in about 18 months - van is not driven much - but when it is used, it sees a fair bit of trailer towing duty.

At what intervals should I change that transmission filter?

 

[GhostFlame]

Originally Posted By: eagle23
If you have the ability, use the Mityvac to drain most of the pan, then drop the pan and change the filter. Dropping the pan filled with fluid is usually the worst part.

Once that's done, you can Mityvac every 20-25k if you want. I'd use it like Honda's 3x drain/refill: drain the pain with the Mityvac, refill fresh the 2-3 quarts you just removed, drive around the block and do it again, 2 more times. You will have replaced >80%, closer to 90%, of the old stuff with new, and your transmission will be happy

I agree with this post this is what I do for my cars. after the first filter change I just drain/pump and refill 3 times every 30K to 50K depending on the car. and then when the filter has 100,000 miles on it I drop the pan and chg the filter.
Some cars like most German cars say the transmission fluid is lifetime(that means the life of the warranty and their responsibility, LOL). Who's lifetime? 50,000 is the tops for me, atf is cheaper than a new transmission.