Changing ATF on a high mileage car

My 96 Legacy has 286,000+ miles on it with origonal motor, trans ect. I plan on using full synthetic ATF to prolong it's life and efficency. I bought the car used and have no idea how old the fluid is. (at least 2 1/2 years-that's when I bought it) It's still cherry colored and does not smell funny. The 4EAT operates fine. But it surely must be changed, It's a maintenance item. I've heard doing a full flush, as opposed to drain and fill, has been blamed for roaching high mileage transmissions. Something to the effect of "The old fluid that's in there now has lost it's detergent ability long ago. Due to the lack of detergent, gunk has accumulated in the system. Flushing out all of it with new fluid will dis-lodge a lot of gunk and possibly clog it's filter and restrict or stop normal circulation, harming or killing the transmission" Is this true? If so then what is the proper way to change the fluid? I want to change it all and a "drain & fill" only does a portion of the total fluid capacity. Do I accomplish this by doing several consecutive drain and fills seperated by a couple weeks of driving? Eventually all the fluid will be new, without the inital shock to the trans that a complete flush will have. How many drain and fills would that take? Or is there a better, safe way. Oh wait! The filter. The drain plug plan just went out the window. That will require attention. Isn't it a screen that I clean myself.

Any recomendations on fluid. I was thinking of Royal Purple Max ATF or possibly Amsoil

The filter is a screen. Should I clean it? The ease of the drain plug is appealing.

if you are going to drop the pan, and i wouldn't bother, i would do it first, and clean it out. there may be sediment in the bottom.

 

but it it doesn't really matter, first or last. it's the fresh fluid that is going to help.

This is puzzling. I'm finding multiple listings for 4EAT filters, not screens. Am I wrong about the 4EAT having a screen and no typical filter? Check out these listings...

https://www.carpartsdiscount.com/auto/parts/96/subaru/legacy/transmission_filters/automatic_transmission_filter_pan_gasket_kit.html?3593=114592

 

http://www.autohausaz.com/subaru-auto-parts/subaru-legacy-transmission_filter-replacement.html

That whole piece shown in your links is the filter. I purchased a similar (maybe the same?) filter for my old impreza when I changed the transmission filter. There is a screen in the filter piece you can kind of see in that picture. You just drop the transmission pan, take the old one out and put the new one in.

Looking at the indentations in the bottom of the pan on my 96, it looks like there might be a magnet in there. Make sure you replace it after cleaning. I will be pulling the pan and changing the filter on mine shortly so I'll let everyone know.

 

Tom

How much fluid do they hold or do you have to add after draining?

Thanks for the link. Thats a large capacity and a small refill I prob should change it a few times.

DO NOT flush your transmission. For the most part, what you have heard is true.

 

Do 3 - 4 drain and fills separated by some driving. I like to wait a week between each one, some people do it at each oil change.

 

With a high mileage transmission, thats really the only way to do it

 

My transmission has about 60K miles on it... its getting a little hesistant and jumpy sometimes.

 

I keep reading two answers, drain/refill trans fluid with a bottle of tran-x or put in a grounding kit(which i dont understand what his does?)

 

Which should i do? both? 99 SUS.

I would change the fluid if I was you I usually never use any type of additives though. Use some synthetic if you want to spend the money I put redline in mine. With a 99 you should have the spin on filter too so change that also.

 

My transmission has about 60K miles on it... its getting a little hesistant and jumpy sometimes.

 

I keep reading two answers, drain/refill trans fluid with a bottle of tran-x or put in a grounding kit(which i dont understand what his does?)

 

Which should i do? both? 99 SUS.

The term "tranny flush" is misleading in itself. The way I've seen it performed is one cooler line is disconnected from the car and each end is connected to the "flush machine". There are no pumps other than the one in the tranny. As the engine runs, turning the tranny, turning the fluid pump in the tranny, the fluid is pumped into the "flush machine" which is nothing more than a big cylinder with a piston. Like a big hydraulic cylinder made out of clear plastic. As the fluid is pumped into the bottom of the cylinder, the piston goes up, pushing clean new fluid above the cylinder into the tranny at the same pressure that the tranny is designed for since the tranny pump is doing it. When you see clean fluid coming into the bottom of the cylinder, you stop the engine and you then have a complete fluid change. Which is really all that you want. The "flush" happens when an addative is added to break up the gunk and varnish in the tranny. Which you really don't need, tranny fluid has so much detergent in it that just having new fluid will do the job. If you don't replace the tranny filter before or after the fluid change, you risk clogging the filter.

The damage or ruined trannys are from lack of maintenance thru the years, not the fluid change. That's why auto manufacturers changes to synthetic or semi-synthetic tranny fluid. With these long tune up intervals and 100,000 mile warranty, people were only chaning the engine oil every 3000 miles because some guy on tv said so. The car makers didn't want to keep spending money on warranty work so they required a "special fluid" which was nothing more than synthetic or a blend.

 

You can exhange the fluid at home with some clear hose and a bucket, search youtube for that.

 

Just make sure that the right kind of tranny fluid is used! Just because the new dexron 6 supersedes the dexron 3, doesn't meen it's better. The dexron 6 is a lighter viscosity oil for better fuel economy. A lighter oil may not be a good thing for a worn older tranny. Read the manual and use the right stuff.

 

Only dropping the pan or draining the tranny will only remove part of the fluid. That is really a waste of time and money. You still have half or more than half of the fluid in the system. Worn, old, dirty fluid. Think about it this way, would you only change half of your engine oil? Bleed out only half of the brake fluid? Change half of the antifreeze? Doesn't make sense does it.

 

 

Your only going to know what condition your tranny and it's fluid are in after you drop the pan or drain the fluid and change the fliter anyway, so start with that first. If you find a lot of metal glitter in the fluid, the damage is done and no amount of new fluid or synthetic fluid or addatives will fix it. If the fluid is in good shape, then just a refill is all you need. Then think about the complete fluid change later once you know exacly what's going on in there.