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 .

[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.