Auto trans fluid, flush or just drain and re-fill?

Question for the collective.

The old wives tale is that you never flush the trans over 100K miles or there will be too much detergent in it and the trans will start slipping.  I don't subscribe to that, but I"ve never owned a vehicle with an auto over 100K miles until now.  I now have an 07 Volvo S60 that I got for my daughter that's currently at 105K miles.  Now, with my Boxter I can't get it flushed as even the local Porsche dealer doesn't have a flush machine, they just drain and re-fil with magic VW/Audi/Porsche secret sauce, that only changes approx 1/3 of the fluid so I"ve done it three times so far over the last 25k miles as they are known for slipping with old fluid in, and it shifts better after each flush.  With the Volvo I think it's regular fluid.  Should I drain and re-fil myself, or take it ang getit flushed.  I'm leaning towards the later, but the borg ust be in agreement on this!

I do whatever the manufacturer recommends. On my Honda, they say no flush but drain and refill 3 times ( 3 quarts at a time). I’ve flushed several other trannys with no issues. There’s a misconception that a flush will cause damage. It’s not a backflush or high pressure. The new fluid is fed in the same direction and pressures that the tranny operates under. 

Volvo uses a semi magic fluid that is quite expensive.  Most of the Aisan transmissions use the same stuff, and there are some aftermarket synthetics that are rated as well. 

I wouldn't flush, but you can change a larger percentage by draining, filling with 4 liters, taking off the return line on the front of the trans, hold it in a bucket while someone starts the car, then shut the car off at the first sign of a bubble.  That pushes the fresh fluid into the converter, and the old stuff out. 

To fend off the "You'll burn it up" comments, well, you won't.  Everything is wet, and you are not trying to transmit any power through the gearbox.

Streetwiseguy said:

Volvo uses a semi magic fluid that is quite expensive.  Most of the Aisan transmissions use the same stuff, and there are some aftermarket synthetics that are rated as well. 

I wouldn't flush, but you can change a larger percentage by draining, filling with 4 liters, taking off the return line on the front of the trans, hold it in a bucket while someone starts the car, then shut the car off at the first sign of a bubble.  That pushes the fresh fluid into the converter, and the old stuff out. 

To fend off the "You'll burn it up" comments, well, you won't.  Everything is wet, and you are not trying to transmit any power through the gearbox.

 

OK, like it.  Is there an 'official' recommended how-to on this?  Or should I go and search Swedespeed?

I've got a friend who runs a pretty well known trans shop, does performance and factory style rebuilds on pretty much everything.

He says if new fluid kills it it was gonna die anyways.

I prefer a drain and fill  (pan drop) so I can get at the filter if it has an internal one.

I've seen quite a few trans flushed around the 150k range with no problems. I wouldn't hesitate at 105k. 

Random thoughts:

BMW is notorious for “lifetime” ATF.  There is an asterisk in the owner’s manual, and that asterisk says “lifetime = 100k Miles”.  I bought my E60 at 136k with sparse records.  I dropped the pan for fluid and filter change at 165k, so percent fluid changed = 100 minus whatever stayed in the converter.  Current mileage 206k and she’s a beaut, Clark.

”If new fluid kills it, it was already gonna die.”  Truth.

Heat is the enemy of the automatic trans.  New fluid manages heat better than old fluid.  End of story.

i “drain and fill” our 2010 Ody, 3 qts of Honda Genuine ATF, with every oil change (7500 miles).  System holds 12 qts, so IIRC this means the average age of my ATF stays at <30k.  Been doing this since 48k.  Currently at 160k with  zero issues.

Adrian_Thompson said:

Streetwiseguy said:

Volvo uses a semi magic fluid that is quite expensive.  Most of the Aisan transmissions use the same stuff, and there are some aftermarket synthetics that are rated as well. 

I wouldn't flush, but you can change a larger percentage by draining, filling with 4 liters, taking off the return line on the front of the trans, hold it in a bucket while someone starts the car, then shut the car off at the first sign of a bubble.  That pushes the fresh fluid into the converter, and the old stuff out. 

To fend off the "You'll burn it up" comments, well, you won't.  Everything is wet, and you are not trying to transmit any power through the gearbox.

 

OK, like it.  Is there an 'official' recommended how-to on this?  Or should I go and search Swedespeed?

Not really.  Part of the trick is to find the direction of flow through the rad.  Most of them ( Note I said most) go in the bottom and out the top.  I have a used hose that I plug into the outlet on the rad, but that may not be ideal for you.  The return lines generally screw onto the top of the front pan, so you can unscrew it there and stick it in the bucket, or you can find some larger hose that can be clamped over the fitting on the rad.  If you take the lower hose off the rad end, you can stick it in the bucket, but its usually not super easy to access.

You stand a reasonable chance of making a mess...

So, how hard is it to change the trans filter?  Just drop the pan → unbolt filter →  replace filter → bolt pan back on?  If so I may start by doing that.  Then doing the drain →  refill method at every oil change for a couple of years rather than the pump it out the line method mentioned above.

I'll work on fitting the tow bar and wiring this weekend, I probably won't do the fluids until next weekend.

While talking fluids, what about the haldex and rear diff.  Are they straight forward and any specific fluid, brand, double-secret awesome sauce snake oil recommended?  

Changing the filter involves trans removal and splitting the trans case.  Aisan figures, If there's enough junk to block the filter, (which is just a screen) you are berkeleyed anyway.

What was explained to me is that as the transmission fluid operates at a high temperature, the inside of the transmission gets coated in varnish as the fluid ages and the detergent additives wear out.  When new fluid is put in with fresh detergent, it goes to work on the varnish and it will likely start coming off in chunks/flakes and get stuck in the tiny passages of the valve body and solenoid packs.  I'd say the risk for your transmission depends on whether the fluid is still bright red, or if it's more in the reddish-brown zone.

I have a relevant anecdote to this thread.

In 2009 we bought a 2003 sienna with 59k miles on it. I asked the owner if he had changed the transmission fluid for  the 60k interval and he hadn't. So I did and every 30k afterward just drain and fill, drain and fill.

These transmissions are "widely known" to break and be "glass". Which is bullE36 M3 if you change the fluid on interval. at 210k miles I changed the filter when I changed the trans fluid. Old filter looked fine. New filter and fluid in, I changed the fluid only one last time at 240k before I sold it to the local mailman last year who is still driving it to deliver mail. Yup still has the original transmission and it is still strong.

I am a believer in drain and fill because I have never lost a transmission that I got with less than 100k miles on it and I treat them all the same. Actually I've only lost one transmission and it was a junkyard takeoff already with a truck that had 190k miles on it when I bought it. And that one went within 6k miles of when I bought it.

light car on fire.  It'll never be good again.. Everything is bad.  - the internet 

Would the above advice also apply to a FWD 2009 S40?

A trans flush will not get the trans any cleaner than a drain and refill.

It's best to pull the pan and clean out the pan and change the filter and refill. This also gives you a visual indication of trans condition.

NOTE the convertor is a centrifugal filter and the gack caught in the convertor will never come out without taking the convertor apart.

Drunken camp fire stories about too much detergent are ignorant displays of "knowledge"?

Transmissions "slip" when clutch apply pressure falls off, if a clutch slips they are usually burned and will fail shortly. 

bentwrench said:......pull the pan and clean out the pan and change the filter and refill. This also gives you a visual indication of trans condition......

But note up thread, there is no replaceable filter in these Aisin trans, it's a mesh that is only accessible when you split the case.  Anyway I've decided, drain and refil next weekend (this weekend is towbar and wiring)  I'll then drain and re-fill either ever, or every other oil change for the next year or so.,