I've been reading contradicting threads about flushing tranny fluid.

[bob3dsf]

+1 on the multiple drain/fills. The tranny cooler line method saves some time, but either will do what you need depending on your comfort level. I'd bet you might not Need to drop your pan, but if it's your first fluid service, you'd get a look to see if there are shavings, clean it and clean off the magnets, etc. In past messaging with BlackWorksInc, he said the tranny filter isn't a service item. The gist I got was that changing it was not necessary, but won't hurt (so long as you don't mess something up in that process, such as stripping bolts, etc.).

When I did my 100k service, I went ahead and bought a case of WS from my dealer (12 qts). I get a good price since I'm a regular (got my reman'd CV axles from them, spark plugs, etc.). Based on reports of how much people were getting out with a drain, I had felt like a case would 4 drain/fills. I kinda forget now, but I think I got almost 4 qts out with a pan drop. I did 2 more drain/fills (I think, I have to go count my left over bottles) and got 3, or 3.25 qts with just draining (no further pan drops). In between, I drove around the neighborhood to circulate the fluid well. On my last drain, the fluid looked almost new (It was a brownish-red on the first, the typical appearance at change time). I decided I didn't need to finish out the case of fluid, and I was worried that I'd come up short by a quart or so on my final and then have to run out to get a last bottle.... That would have been a PITA.

Anyway, it's not hard. just time consuming, and the "check fluid dance" with the OBD jumper/shifty thing can be frustrating, esp. when you go to check it and it comes up too hot and you have to go wait till it cools to check the level properly. Why oh why couldn't they stick with a dipstick?!? I'm planning on doing the tranny cooler line method at 150k. If you drop your pan, just make sure you don't schnocker your gasket or over tighten the pan bolts. Oh, and don't be in the path of flow when you drop it, you'll think it's level then it'll shift a bit and all the fluid will want to pour all over you. Luckily I was ready for it, but I almost messed up my driveway....

 

[07V8]

Well I completed the coolant line flush last tonight. Let me be the first official report of a catastrophic failure from a fluid exchange on a A750F. I started the car after finishing, put it in gear, and the transmission fell out of the car……I really have no idea what happened, the transmission housing sheared right off the mounts.

Now that I’ve got your attention, I spent 4.5 hours last night completing the procedure outlined on the first page. I took an excessive amount of time doing everything and had to be extremely neat because I was doing it in my high rise’s parking garage.
I started by cleaning all the plugs with Simple Green, I wanted to ensure any grime/salt/debris was cleaned – especially near the fill plug. I then tested each plug by cracking it open. My 12 point socket was slipping on the 24mm fill plug so I had to take an Uber to Napa to grab a 6 point socket. While there, I also found a hand pump that screwed into the WS bottles: a huge find! The 4cc Plew’s pump from Amazon would have driven me insane because of how I was positioned under the car and the fact that any bottle movement would have resulted in spills.

When I drained the pan, a little less than 3 quarts came out. As it was draining towards the end I rocked the car back and forth to get as much as possible out. The fluid was brown/maroon-ish but really didn’t smell burnt or look too bad. Buttoned the drain plug with a new crush washer and proceeded to repeatedly flush the transmission out through the coolant return line.

All in all, I used 14 quarts of WS, I wanted to visually see new fluid coming out of the return line before calling it good. I marked up a gallon water jug and pumped 2-3 quarts out each time. I did my best to estimate how much to put back in, I spilled a little and the hand pump left a little bit in each bottle the volume in the hose. On the last cycle, I added an additional quart.

Lastly, I started the car, let it idle, and was so happy to have some fluid squirt out of the level plug. I used my SG II to monitor temps and popped the plug when it read about 100°F in the pan and the torque converter. About a half quart had drained out when it started to trickle. I replaced the plug with a new washer and tightened everything down.

All in all, it was an extremely easy job. The hardest part was the ergonomics working underneath the car. Luckily, the concrete cleaned up easily and brake cleaner worked wonders on any residual spilled product. Considering I have never done an oil change on my car, I’m extremely proud of myself for tackling this. I know it was done 100% correct with lots of TLC which is way more valuable and stress free than leaving it with the dealer.

Post fluid change driving dynamics are essentially unchanged. Overall transmission performance when cold (fluid <120°F) seems smoother, especially the 1-2 shifts; however, everything else is essentially unchanged. Most of what I think I feel is placebo. Going forward, I will do a drain/fill every 15k (two oil changes for me). I don’t see any value in dropping the pan. The filter (rather large metal screen) will only stop the largest of debris/shavings from being recirculated.

Do not hesitate to do this – especially on higher mileage transmissions. There really is no way you can damage anything so long as you remember to pump fluid back in the transmission. As a Machinery Reliability Engineer, I have to recommend you stick with the OEM fluid recommendation – especially since there is no real data on exactly what it is. Viscosity comparisons and MSDSs are phenomenally insufficient when deciding on a fluid for a critical rotating machine. Good luck!

 

[MFreund]

I did a return line fluid exchange yesterday. 198300 miles. I am not sure it had ever been done. At first it was very dark and smelled almost burnt. The reason I think it has never been done? I had to use a impact screwdriver to get the 5mm check plug out. I had the torque convertor shudder.I hope the transmission lasts, but if it does not I will report back. On the top is original fluid, bottom new fluid.

 

[RockyRider]

Did they do it themselves or have a shop hook a pump up to it.

A shop pumped it out. I don't know what tool or system they used, but the fluid was brand new and clean when I checked the transmission after it began slipping.