Roger Needham

I know that there is a correct procedure but is it possible to successfully swap out fluid by pumping out via dipstick tube. Purely as a temporary measure?

dvs_dave

The transmission on the A8 doesn't have a dipstick. Only ways to do it are via the oil cooler lines, or dropping the trans oil pan.

bmwm750

You could if the gearbox had a dipstick and/or dipstick tube.....

Likewise, I'd hope that you realize that Tiptronic or not (which all D3's are), it's still just a ZF 6HP automatic transmission, so there's nothing special about it being "Tiptronic."

The only practical way to do this is by dropping the pan.

mishar

You do not need to drop the pan. There is a drain plug close to the front of the pan. It will drain about 5.5 liters. That's just a bit less than when you drop the pan.

bmwm750

Why swap fluid without changing the filter and cleaning the magnets?

MP4.2+6.0

One of the worry areas on a drain and replace is the theory than a renewed fluid additive package can start to break loose existing built up crap inside the tranny. Having been inside my C5 A6 4.2 ZF 5 speed for a couple of fluid changes, the metallic sheen and light gooey sort of coating over most everything imaginable was pretty obvious. Thus, I would want a clean filter for starters with some built up miles and crud. If I'm doing a multicycle drain and replace, maybe not on the later ones in fairly short order, but definitely I would prefer to change the filter and clean the magnets on the first go around. As a W12, I'm also in the "blue"/6+ fluid realm so unlike conventional original 4.2 "gold"/6, I don't have to debate the 6+/8 upgrade that would suggest getting the fluid nearly fully changed out.

In the practical world BTW, this remains on my to do list. At least on the W12, actually getting that pan out looks like a challenge, so it could default to mishar's take absent a boatload of pain or some new tricks. The exhausts are meaningfully in the way of the pan on a W12, probably more than the D3 4.2, and definitely more than my C5 4.2. I'm not sure it can come out the normal straight down with a little angling as you go (and face/armful of last fluid) method. I think Bentley says drop the head pipes on the W12. Since that isn't going to happen in my world (pain in the a#@ enough on my C5 for motor work let alone the 4 into 2 exhaust with bigger pipes of the W12), I'm still contemplating plan B. Since I am also after the gear oil change in the forward and center diffs, it may be the grandiose drop the W12 gear oil and aux. water to fluid coolers if the tranny pan hangs up on my way to pulling it. And those aux. coolers are...just in front of the tranny pan on the W12. It thus also opens up forward direction pan removal scenarios where the down pipes are more spread out and that are not otherwise possible with those coolers in position. Undocumented as far as I know, but I've got the various fluids and (few) necessary seals in my standby supplies box. Hasn't made it to the top of my to-do maintenance list yet, but once I confirm my fail safe that I can get to all applicable fill ports reliably (not a given on a W12), it's may end up being the trifecta of near simultaneous tranny, gear and engine coolant changes. I think the W12 has inter-tied common gear oils both front and rear (center)--which means the expensive stuff connected to the Torsen throughout--but worst case I figure if only one drains but I can get to both fills, if I open a fill (or drain) port and find it still full I will know they aren't actually tied together and I will just proceed accordingly.

MP4.2+6.0

Has any W12 owner actually done the tranny pan drop with everything in place (tranny in car, surrounding exhaust not removed, no trick lifts or things do able only with car on a full shop rack, etc.)? If not a W12, how about an S8 since they have a very similar exhaust set up, and perhaps have both aux. coolers just forward of the tranny pan too?

It dawned on me to at least ask before I head off to the unknown avoiding any heavy exhaust dismantling. Not ultimately being able to get at the filter could cause me to leave it to be unless I'm pretty confident in my aux. cooler removal end around. See my preceding reply for that nuance/proposed trick.

TSHong

I don't think it's possible without some exhaust dismantling. The reason my transmission was so low in fluid when I go the car, was that the pan was leaking. There were two very loose bolts and after tightening them, no more leaks. The loose bolts were a TSB I found and I hit the jackpot when I discovered them being loose. One of the bolts was behind the exhaust, so we bent a wrench to get to it. There is just no room without taking the exhaust apart.

bmwm750

Based on the few times I've been under a W12, I would fully anticipate that you won't be able to get the pan out without pulling the exhaust, which looks like a HUGE PITA.

mishar

I believe that answers the question why just drain whatever can be drained and refresh it with 66% of a new ATF. Dropping pan on V8 is possible (I did that), but no fun and I wouldn't let just oil guys do it. So it becomes expensive. By the way, magnets and filter where clean.

I am puzzled by TSHong's "case" of 3 quarts low ATF. Transmission was obviously still working, what brings a question: how important is that temperature fiddling at the final level setting?