Auto transmission fluid getting dirty... how to replace?

[ryu_haneda]

Hey all,

my gt sedan needs its auto tranny fluid replaced. I've quoted a few places already, and have gotten two VERY different quote prices: one for a "power flush" (subaru dealers have told me this), and another significantly cheaper price for a drain and refill.

What's the difference? Does it r-e-a-l-l-y matter if I powerflush as opposed to having someone simply drain and fill my tranny fluid?

By the way, when I recently had my car get a diagnostic check, the Subaru dealer I got diagnosed at said that my throttle body was slightly "out of whack" (i.e. this is why I get slightly clunky or rough shifts from 1st to 2nd gear in my auto tranny). Is this something I should fix immediately? Could this have aggravated my AT fluid going sour sooner?

[Huffer]

Do NOT get a powerflush. You run the risk of contaminated fluid being forced into areas inside the transmission. Many AT flush machines are never cleaned out properly.

All you need to do is buy enough ATF for 2 changes - about 8quarts I think.

Warm the car up, put it up on ramps and drain the tranny. You'll get about 4 quarts out. Put more ATF in via the transmission dipstick tube (I recommend a long thin tube for this and take your time). Back it off the ramps and go for a drive. Stop the car, push the gear shifter through all the gear selections.

Go back onto the ramps - repeat the above procedure.

Once you're back home, check the ATF level and top it up if necessary - and if you want to preserve the transmission, add a bottle of LubeGard ATF Protectant (red bottle). Lubegard is a friction modifier, it will also help lower the overall temperatures of the transmission. This will lengthen the life of the transmission.

There is one way to do a "flush" and that is to hook up a hose to both the drain pan and also the dipstick - you ensure you have fluid going into the dipstick at the same time you have fluid flowing out of the drain pain - and the engine is running. When the fluid runs "clean" then you shut off the engine and stop the flow of fluid.

I like my original method more - it's more involved, but it's less messy and more predictable.

BTW. the dealership is BSing you about the "clunky" shifts. Subaru 4EAT trannies are hard shifters regardless - but you can help things by refreshing the fluids.

[ryu_haneda]

I think I'll just go with a drain and refill, and KEEP about 85+ dollars in my pocket. I'm glad I was shopping around.

[TRUBLU]

Don't confuse a powerflush with a fluid exchange. The second flush that huffer mentioned is THE power flush and is heavily advised against. This will push the contaminants and varnish ALL OVER the place inside the transmission.

A fluid exchange is ideally the best method to use if the transmission is done on a regular basis. (Every 30,000 miles on Subarus.)

A fluid exchange is done by using This machine http://www.mytoolstore.com/clore/ttech.html

One line is hooked upto the fluid line that runs TO the radiator whilst the other one is hooked upto the line going INTO the radiator. The machine is then filled with enough ATF to fill the vehicle. The car is then started and left in PARK. The transmission own internal pump will force the fluid towards the radiator cooling lines. Now instead of going into the radiators transmission cooler, it is now fed into the line to the T-Tech machine filling the lower half of the tank. As the fluid is pushed in it moves a big valve upwards forcing new fluid back down the line returning to transmission cooler and slowly pumping itself through the cooler, down the lines and into the transmission. The process is completed when all of the old transmission is exchanged and ATF is being pumped into the machine.

This method provides about a 99% fluid exchange. By draining the pan you will remove about 30-40% of the fluid actually required.

Now, having said all of this, many people don't like the method I explained above. Heres why, they drive in a car with 150,000 miles on it and the last time a transmission exchange was performed was well over 100,000 miles ago. Thats a lot of shit inside that transmission. Varnish is all over the place (almost keeping the thing together) Contaminants are everywhere and the transmission is starting to slip. Also, the pour point suppressants are shot to hell, the detergents are gone, the oxidization inhibitors are gone and the internals are starting to rust. Now, the big thing.....the Hydraulic Pressure abilities of the old ATF has degraded as well as the transmission. Your push in all this new fluid and the hydraulic pressure goes through the roof causing damage to the transmission. This is a highly unlikely event, but it can happen if the transmission has had it's preventative maintenance done on the regular basis.

Now, if you have had the transmission serviced in the last 100,000 miles then I say the exchange is the only way to go! If it hasn't then you need to be doing a drain and refill. Only do it once though. Then in about 7-10,000 miles. Do it again. Do this three times and then start doing fluid exchnages every 30,000 miles like you should be doing.

Also, with Subarus, anytime you change the ATF you should also be swapping out the filter. Filter you say? Yes, all transmissions have a filter. On subarus it's actually a spin-on filter just like your oil filter! It's located on the drivers side towards the front of the transmission. Make sure when you replalce it that you tighten it with a band wrench...that sucker HAS to be tight!

[Huffer]

Also, with Subarus, anytime you change the ATF you should also be swapping out the filter. Filter you say? Yes, all transmissions have a filter. On subarus it's actually a spin-on filter just like your oil filter! It's located on the drivers side towards the front of the transmission. Make sure when you replalce it that you tighten it with a band wrench...that sucker HAS to be tight!

I was believing everything you said right up until that point.

Some Subaru's (earlier models, pre-2000 usually) don't have spin on filters. They have an in-pan filter that requires the pan to be dropped off.

[TRUBLU]

Pre 96 don't have a spin-on.

[Huffer]

Pre 96 don't have a spin-on.

Pre 99 as well. I should know, I own TWO - manual AND automatic.

[TRUBLU]

Interesting! You better nt tell that to my 99 or the 97 I had before this one.....I changed both their filters multiple times! Didn't realise there was any differences but mine defineetly had spin-ons and yours didn't....learn something new everyday eh?

[Svenerachi]

mine doesn't have the spin-on either

[TRUBLU]

Ok, so I did some research at work today and it was an interesting find! It appears that Outbacks have spin on filters and regular Legacys do not.

I pulled out my manual also and it shows that under normal driving conditions my transmission fluid should be changed every 30,000 miles as well as the filter. But, if it goes under extreme conditions then th fluid should be changed 15,000 and the filter changed at every 30,000.

Why Subaru went to the effort of creating different transmissions for essentially the same vehicle I'm not sure.

[ProdriveDreams]

Now, having said all of this, many people don't like the method I explained above. Heres why, they drive in a car with 150,000 miles on it and the last time a transmission exchange was performed was well over 100,000 miles ago. Thats a lot of shit inside that transmission....You push in all this new fluid and the hydraulic pressure goes through the roof causing damage to the transmission. This is a highly unlikely event, but it can happen if the transmission has had it's preventative maintenance done on the regular basis.

Another problem that arises is that the old fluid has become gritty and full of small particles and these wear away the straight cut valves in the valvebody, which seal using simple clearance. The old fluid is too thick to sneak past these larger clearances, but fresh fluid is allowed by, and causes hard/no shift condition, and occasionally slippage.

[TRUBLU]

Yup, that too!

An older gentleman insisted that I do the exchange on his F150 with 210XXX that had never even had a pan drop, just continually topped off through out the years. Unfortunatly, the truck never even left the shop before its transmission died. Furtunatly I had him sign a disclaimer stating that warranty was given due to mileage.

[boxerpower]

if its a filter just like the oil filter it should only be "snug" not so tight that you have to use a wrench to make it tight. the o-ring can distort under too much pressure resulting in an oil leak. or the can of the filter could crush.

[TRUBLU]

I'm going to have to disagree there...but that really doesn't matter! They have a larger gasket because they are required to be tightened down.

Only what I was taught though...always open to new ways!

[Huffer]

Ok, so I did some research at work today and it was an interesting find! It appears that Outbacks have spin on filters and regular Legacys do not.

I pulled out my manual also and it shows that under normal driving conditions my transmission fluid should be changed every 30,000 miles as well as the filter. But, if it goes under extreme conditions then th fluid should be changed 15,000 and the filter changed at every 30,000.

Why Subaru went to the effort of creating different transmissions for essentially the same vehicle I'm not sure.

That's interesting... does it have anything to do with the idea that an Outback might actually do more "work" like towing and going offroad?

[TRUBLU]

Ok, so I did some research at work today and it was an interesting find! It appears that Outbacks have spin on filters and regular Legacys do not.

I pulled out my manual also and it shows that under normal driving conditions my transmission fluid should be changed every 30,000 miles as well as the filter. But, if it goes under extreme conditions then th fluid should be changed 15,000 and the filter changed at every 30,000.

Why Subaru went to the effort of creating different transmissions for essentially the same vehicle I'm not sure.

That's interesting... does it have anything to do with the idea that an Outback might actually do more "work" like towing and going offroad?

That was the first and only thought that came to my head.