Automatic Transmission Fluid Changing Strategy -- Opinions Please

[Victor]

Having read the pro's / cons of changing auto trans fluid, consensus seems to be:

- if it's been changed (at least once / 60k mi.) it can probably be safely changed again. No worries.
- If it hasn't, could destroy trans with one change. (Me... Worries).
- Flushing is not recommended under either circumstances.

Mine may never have been changed, though the trans works well now. Not looking to mess it up!~ ('95 525i 139,000 mi. auto trans, model: A4S 310R).

Tentative Plan:

1) Change filter, pan gasket, securing nuts.
2) Replace only 1/2 - 1 liter of fluid as a test.
3) Drive car 500 mi before changing more fluid.

If new issues begin, hold breath and prey it doesn't get worse. If the trans feels happy, change out another liter. Drive another 500 miles. If this continues to seem fine, then (and only then) do a bigger change.

It's a lot of trouble, but the alternative of ignoring the fluid until the trans dies is hard on my brain cells. I want to approach changing the fluid without taking tremendous risk.

Any thoughts on my procedure?? Thanks, Vic

'95 525i 139k mi. Owned 3 months.
'86 Benz, 420SEL. 110k mi. (Father was original owner).

[Tiger]

There is no con for changing fluid. If you have major slipping now, you know it is already damaged. My friend had a tranny that slipping so bad and burnt fluid, changed the filter and fluid... transmission ran good for another 20000 miles before it died completely.

My diesel, was stuttering from accelerating when I first bought the car... I had full history but tranny was not really taken cared of. Changed out the fluid and filter, car ran great... still working great.

My BMW had zero fluid change for over 100K miles... I changed out the fluid and filter and it ran even better.


I would change your fluid by flushing it out... just drain your fluid and refill it with Valvoline ATF... regular stuff... and drive it for a while... a week or two... and do the job again... drain it and refill it with new fluid and drive it again for another week or two... Then drain, drop the pan, change filter and refill with new fluid and you are done.

You will be able to tell if your tranny runs better on first change.

[Russell]

Having read the pro's / cons of changing auto trans fluid, consensus seems to be:

- if it's been changed (at least once / 60k mi.) it can probably be safely changed again. No worries.
- If it hasn't, could destroy trans with one change. (Me... Worries).
- Flushing is not recommended under either circumstances.

Mine may never have been changed, though the trans works well now. Not looking to mess it up!~ ('95 525i 139,000 mi. auto trans, model: A4S 310R).

Tentative Plan:

1) Change filter, pan gasket, securing nuts.
2) Replace only 1/2 - 1 liter of fluid as a test.
3) Drive car 500 mi before changing more fluid.

If new issues begin, hold breath and prey it doesn't get worse. If the trans feels happy, change out another liter. Drive another 500 miles. If this continues to seem fine, then (and only then) do a bigger change.

It's a lot of trouble, but the alternative of ignoring the fluid until the trans dies is hard on my brain cells. I want to approach changing the fluid without taking tremendous risk.

Any thoughts on my procedure?? Thanks, Vic

'95 525i 139k mi. Owned 3 months.
'86 Benz, 420SEL. 110k mi. (Father was original owner).

Change the fluid and filter. Blow out the oil cooler lines with air. Use Dextron VI trany fluid. I use Valvoline. This will replace about 1/2 the fluid. Keep in mind that the 95 has no dipstick and fulid level must be checked when level and at a specific temp. Not much fun without a lift. FYI, I change mine every 30,000 miles.

[John B.]

I've done our 95 525iT several times & as was already stated it wasn't fun but I do have a lift. Can't say I really enjoyed standing under a running car holding a temp probe waiting for the fluid to hit the right temp but as jobs go it certainly beat changing the clutch by myself in our 535i without a tranny jack. Follow the procedure outlined in the Bentley unless you can measure every drop you remove. You will have to dump, refill, drive several times to get all the dirty oil out of there as it is but doing one liter at a time would be crazy.

[Bill R.]

I've done many of them also, with a lift and without a lift. The biggest hassle without a lift was getting the car level on 4 jackstands. I put a small level on the bottom of the transmission pan to get it level on e46's.... on the older cars i use a infrared thermometer and just read the temp off the bottom of the pan. With ambient temps here in the 90f to 110f range it doesn't take much running time at all to get the fluid to optimal checking temp. I have more problems getting it full before the temp goes too high and messes up the level reading..... If that happens i have to shut it down and wait for it to cool back down to the best temp. The newer obdII cars i can use a scan tool to measure the trans fluid temp and do the final fillups just as its reaching the optimal temp.

I don't flush the system, i just do repeated drain and fills... Drain car fill at temp. Run it for 5 or ten minutes on the lift or on the jack stands going through the gears repeatedly. shut it down and drain again, repeat etc. It took about 24 quarts of ATF the lastime i did the e46... When i had to repair the e46 trans, it didn't take nearly as much since i could blow the trans cooler out with compressed air and chemical flush. I also was able to empty most of the torque converter out so it really didn't take repeated drain and fills that time.

[Victor]

Thanks all for such great replies. Specific questions for each of you follow, but generally:

- My post is about a strategy for avoiding the sudden death of the trans syndrome often described after the fluid is changed. As the trans holds 8.8 L (including torque converter) a simple drain and fill is already fractional (3 L). Yet sudden trans death is often reported. This could be due to several factors: 1) Inaccurate level, 2) detergent in new fluid mobilizing gunk previously stable, 3) detergent in new fluid mobilizing trapped material in filter (if not changed).

4 Grand Master - Are you saying it's OK not to change the filter on the first drain / fill?

Big, Big Time Poster - I have 139k mi. and you're recommending a complete drain / fill of fluid initially. No fear, huh?

Super Moderator - What does blowing the trans cooler line do and how did you manage to use 24 quarts??

Thanks to all.

[Tiger]

Ot os absolutely okay NOT to change the filter on the first drain/fill. Transmission filter is a simple filter... nothing special about it. If it is clogged, it will simply bypass the filter... just like oil filter. The reasoning to NOT change the filter is to get as much gunks out of the transmission so it won't clog the new filter right away. So by drain and fill two times, you pretty got most of the floating matters out of the tranny.

You have to take the internet posting with a grain of salt... some will say whatefver they want... some had trouble with tranny or didn't know they had trouble with tranny and then the tranny failed with new fluid and filter... you get the point.

[eason]

Good and informative post. Thank you! I learnt a lot!

[Bill R.]

Normally the transmission cooler will hold some of the deposits and gunk that build up, so on a normal drain and fill you have to repeat it often enough to clean out this line with transmission fluid. When i pulled the transmission out of my wifes e46 touring, it was much easier to blow air and chemical flush through the cooler until it was very clean. This transmission is a ZF5hp19 or if you use bmw nomenclature A5S325Z. When i took it apart to repair it ,it was easy to get all the fluid out of the valve body and the torque converter and i cleaned out the inside of the transmission while it was apart. Upon reassembly It only took the normal amount for a complete fill.
When i did a drain and fill earlier on that same car it took a lot more since i drained it ,took the pan down and cleaned it, changed the filter and then filled it.

Approx 4 quarts at that point, then ran it for ten minutes, drained it looked at the color, the new fluid was dark again, filled and repeat until the fluid was clean coming out. Thats why it took 24 quarts of drain and fill until it was clean coming out. I was using castrol import atf which met the specs for the zf5hp19. On the rebuild/repair it took a lot less because it was clean to begin with. You Strassbourg transmission takes a different amount of fluid.
When you first drain it and if its absolutely black with a lot of shiny particles in it, thats when what you call sudden death is more likely to occur. I've seen it most commonly on fords with very high mileage without a fluid change. Usually there was a problem with how it drove which prompted the customer to decide to have it changed. After changing when the trans fails shortly afterwards the customer of course blames the shop. Odds are that since it already had a problem it was going to fail soon anyway. If your fluid is just dark but not a lot of particles are present then a normal drain and fill will be fine.

[Victor]

Thanks Bill. Do you think you could explain why fluid which is bad (black, particulate, other) is riskier to remove? It would seem the worse it is the more benefit there is to getting it out. If replacing particulate fluid could kill the trans, then even replacing the filter could be a bad idea.

Moreover, my post is about establishing a conservative strategy. I hadn't considered fluid inspection, but maybe I should. I was just going to change a small amount, see how it goes, and keep changing if all is well. If I understand your post correctly, if it's black and shiny particles are within, I should just put it back.

[Tiger]

All transmission fluid will have particulates... it is from the friction materials in the transmission. Mine was super dark brown with tons of particulates. No burn smell.

When you do the tranmission filter job, you will understand why it is pointless to be 'conservative'... there is just too much work and effort to do that little thing. Get under your car and see how much work you have to do to implement your plan.

[Victor]

Here's a reply from the NJ BMW club tech contact. Not sure, but think he's had pro repair shop experience:

Victor,

I get asked this question quite often. Fooling around with a 16-year-old auto trans with 139k and no service history is, to me, a crapshoot. I think I would leave it be.

There are other knowledgable BMW folks who disagree and who would tell you to try servicing the trans. Some recommend replacing one quart of fluid at a time. If you decide to fool with it that is what I suggest.

[BMW4LIFE]

Some may tell you to never touch it...but I have had GREAT luck changing mine!

Just make sure you do not FLUSH it!

I went to costco and bought a case of the Chevron Dex III and ordered a new filter.

I did an initial drain of the old fluid, closed it, poured new fluid in, closed it, and drove about 100 miles

Then I drained it, closed it, filled it, closed it, and drove another 100 miles

Finally I drained it, DROPPED THE PAN (both small and large), cleaned them out including the magnet, changed the filter, got a new gasket for small and large, filled it and Loved every second of the change!

Mind you that I did this when the car had 180k or so on it and I assume that it had never been changed before...now it shifts smoother than ever!

[whiskychaser]

Here's a reply from the NJ BMW club tech contact. Not sure, but think he's had pro repair shop experience:

There are other knowledgable BMW folks who disagree and who would tell you to try servicing the trans. Some recommend replacing one quart of fluid at a time. If you decide to fool with it that is what I suggest.

IMHO this is an urban myth and Bill R hits the nail on the head: if it fails after an ATF change it was going to fail anyway. Is the dirty ATF or swarf supposed to be holding it together? ;)

[genphreak]

Remember BMW techs opinions come from working in a dealership, where they should do no wrong (else suffer their manager's wrath), and where more than 50% of the cars coming in are new, and most of the balance are there as they have a problem already.

I don't feel that such opinions are statistically accurate for our cars- they are not the same demographic (i.e. how many 20yo Bimmers get serviced/fixed at BMW now?).

[Bill R.]

Its definitely not a myth, i've run into it too many times on older fords. Speculation is that you get gunk buildup behind the old orings and pistons that help it to seal, when flushing the the trans fluid the detergent action of the new fluid cleans and removes this buildup and the old orings no longer seal , fluid pressure goes around them etc.... or the detergent action flushes buildup out of areas that are past the filter and the gunk moves into the valve body and plugs up pistons and solendoids that have very tight tolerances..... take your pick. Either way i've seen really gunked up transmisssions fail after the fluid change.... Odds are they would have failed anyway but the customer still tries to blame the shop/mechanic for the failure... In my mind if the customer suddenly decides to change the fluid at 150k when he never bothered to have it changed ever before then he or she has noticed some kind of symptoms that may have already signaled impending doom for the trans.

[Russell]

Remember BMW techs opinions come from working in a dealership, where they should do no wrong (else suffer their manager's wrath), and where more than 50% of the cars coming in are new, and most of the balance are there as they have a problem already.

I don't feel that such opinions are statistically accurate for our cars- they are not the same demographic (i.e. how many 20yo Bimmers get serviced/fixed at BMW now?).

That said, I trust Bill R's opinion.

[Victor]

With respect to both Russell and Bill's comments, the original question regarded developing a strategy for NOT screwing-up the trans when history is unknown. The concept of incremental fluid changes has been given sufficient pro / con discussion, but the trans fluid color / condition question less so. Red, black, particulate, metallic ... Each has some meaning.

In my case my indy said my fluid "didn't look too bad." I don't have records, but assume if it's not too bad that a change will extend its life. The plan as it stands is:

1. Remove a small sample of fluid. Note condition (which I'll report here). If not really scary looking, replace a quart. (I bought a pump for the purpose). Otherwise, the glop goes back in. (I wish I could properly check the level, but without a lift it's impossible as the trans will be crooked).

2. Assuming I've made a small replacement of some fluid, off I go on my test. Next replacement may be the same, or larger, depending on original fluid color and driving results.

3. After confidence builds, replace filter, gasket, and all fluid from the pan.

If the fluid is not awful, but not great either, I suppose there's the possibility of dislodging gunk once the new fluid's concentration reaches a certain point. Of course I could stop if I feel I've pressed my luck.

[BMW4LIFE]

I want to say that I get where your paranoia comes from but at the same time it still blows my mind how people will consider keeping 20 year old beaten fluid in the trans rather than pouring in clean fluid.

I hear what you are saying about it failing after the change, but like people have said before, if the NEW fluid RUINED your tranny, that ish was on its way out! Its like saying...My engine run...why should I change the oil? I mean, what happens if when i change it the engine blows up? Idk....I was very paranoid as well but after A LOT of research I noticed that the fluid changing wasn't the culparte here...rather the FLUSHING that is done under pressure. If you want to be REALLY REALLY cautious, I would do my procedure but one quart at a time...might take you longer than anyone would have patience for but the progression would be sooo slow that you wouldn't notice a difference.

Furthermore, if your tranny is held together by GUNK...well, better it fails on you when you expect it than when you are climbing the road 300 miles away from you house...

p.s. that is not suppose to scare you...

Change it and be done with it!

[Victor]

BMW4LIFE,

You got away with a full fluid change on a 180k trans! Quite impressive, flying in the face of conventional wisdom which holds that if you don't think it's been changed, as you assumed, don't change it (due to internal build ups which can become dislodged). Interesting that you say flushing can be the culprit. Why wouldn't the same logic hold, that flushing could only be good?

Again, in my case I don't know if it's every been changed, but I'll take a sample soon and see if I learn anything. The better it is, the more confidently I'll change the fluid.

Best, Vic

[BMW4LIFE]

Well I am by no means a transmission expert but I will tell you what I know...


Flushing is a forceful act that forces out the old and inserts the new...This is when dislodging is prone to happen when a FORCED fluid is pushed through the transmission. Now with the drain and fill technique you are not forcefully pushing new fluid in rather gently baby feeding it in. The chances of dislodgment are lessened with avoiding the flushing.

Now if you are paranoid still here is another thing you can do. Drain your large pan, drop the pan, look at the magnet inside the pan, if you have sooo much excess metal shavings that the magnet looks like a donut, well you may have a tranny issue sooner than later regardless of the change, but if the magnet has a slight to somewhat amount of shaving (which is normal wear and tear) well then start changing it slowly.

The only thing I remember that was a really bad sign from you old fluid was that...if you smelt a burning smell. If so...OH OH...if not (as in my case) change the fluid out, enjoy your tranny with clean fluid, and finally come back and laugh about this thread on how silly keeping old fluid in the tranny is.

That whole, "don't fit it if it isn't broke" is gibberish!

Lastly, Honda, does not want you to flush their tranny rather ONLY require you to fill and drain.

In my eyes, I think if you flush your tranny every 30k since the car was new...that may be okay...in any other situations I would play it safe and do the drain and fill method.



p.s. There are smarter people than me on this forum, but my vote goes to change it (if it doesn't smell burnt and/or a lot of metal shaving on the magnet)!

Now time for a vicodin and a pillow for my gimpy foot!

[genphreak]

I doubt the flush does the damage, more likely when it is done, the pressure is not maintained and the tranny runs a bit low on pressure- or there is a temperature shock or some such change which can actually damage the friction surfaces- or clog orifices, etc.

When combined with a shot trans (eg the clutches are already about to let go), might precipitate a failure. We all know that fluid with particulates in it cannot make up for worn surfaces- or allow a trans to stay in service any longer.