My 2018 F56S 6-speed auto seems to be developing a transmission issue at 45k miles. Correct me if I am wrong, but in regular "drive", the car starts out in second gear, unless you aggressively stomp on the gas pedal, then it shifts into first and launches. The issue with my 2018 F56S auto (Aisin 6F21WA, I think) is that twice now I have stomped on the gas from a standstill in Drive and it has seemed to "slip" and then BANG into first gear very violently. Like nothing happens, then there is this violent BANG and it takes off. It has happened twice now, once when cold (around 130 F coolant temp) and once when up to operating temp. I did have the Sport Transmission option coded into my PCM remotely like 6 months ago, and it seemed to make a big difference in shift firmness, but this is a new thing, like it's happened twice now in the last 2 weeks or so. Anyone have such an issue? I plan to have that Sport Trans removed, then take it to the dealer, since it is still under warranty until 5/23/23. I did do a fluid drain and fill at around 25k miles, and I used the proper trans fluid and the proper amount. Thanks for any help/info/advice y'all can give.

 

Well, you already did the first thing I would have suggested and you did it 20K miles ago -- fluid drain and fill. Curious as to what fluid you used?

My 2017 F56S (confirmed Aisin GA6F21AW) didn't throw any obvious transmission problems, but at 101K when I changed the fluid out one of the first things I noticed was more frequent use of 1st gear and incredibly more routine stepup from 1-2 by the transmission. Prior to that I would not even have guessed that my AT was "bottoming out" in 2nd gear. This sounds curiously akin to what you describe (though I never had the "BANG" experience you reference).

Important note, I do not have the Sport Transmission nor have I had that option coded (never thought of that...), so take my experience for what it's worth under your best judgment.

 

Might not be a solution to the issue, or maybe a partial solution to prevent further problems if the 3rd Gen Aisins allow it, but on my 1st gen Aisin auto you can pre-select 1st gear while stopped instead stomping on the gas to get it to kick down from 2nd.

I’m not sure if the 1st or 2nd gen Aisins kick down on takeoff since I’ve never tried it.

 

Does this "bang" happen when you press on the pedal normally or only when you "aggressively stomp" on it?
Have you checked the transmission mount and bushing? From my understanding, it's a similar setup as the engine mount but lower and obviously on the other side of the engine bay. Just a thought that maybe the transmission shifted due to the mount/bushing going south and thus it's harder for the transmission to enter into 1st gear, especially with the sport auto being coded in.

 

What mileage are you at currently? I've always wondered about changing out the fluid at a higher mileage. I had been informed (possibly wrongly) that the ATF should be changed (if it was going to be) by 40k miles and if it were done later on it would increase the likelihood of issues within the transmission because the transmission gets used to the particular viscosity of the ATF.

 

It only happens (and only twice now) when I stomp the go-pedal pretty hard from a dead stop (like 1/2 throttle) and the trans kicks down to first. I actually haven't eyeballed the trans mount yet, but will do so. I have now returned all programming to stock, and will make an appointment soon with my local dealer, as my warranty is about to time out. Thank you.

 

Changed it out at just over 101K miles. Currently at 102.6K.

"Don't change your ATF" and its cousin, "don't go from dino oil to synthetic" are both really old and closely related bits of guidance. The whole viscosity-getting-used-to thing is a variant (IMO) of same.

My personal take: if the fluid is synthetic it's not supposed to "gum up gaps" and all that other stuff in a transmission or an engine or any other application, and that notion of the fluid "gumming up gaps" created by wear and tear is central to both guidance sets. In the case where nothing but synthetic has ever been run and there isn't abnormal or severe wear and tear in play, there should be precious little variance from doing a drip-drain/refill method fluid change. I would expect that to especially be true if using the same fluid spec as original. In my case I used AISIN fluid, and it's an AISIN-manufactured transmission, and this fluid is specced for that particular AISIN transmission. Not much to go wrong there.

Further and maybe more importantly, let's be real -- there are repair scenarios where you have to drain fluid to do the work. That means you refill with new fluid, not old. If those cases resulted in "oops you changed the fluid now you're going to bake the tranny that was used to the old viscosity/etc." then nobody would be able to get such repairs done successfully.

If we were talking an old-school transmission (pre-1990 maybe) and original spec of non-synthetic ATF I might be a small bit worried about this. But on a 2016-built transmission (my 2017 was manufactured in late 2016) that got new syn fluid of the same spec as was put in it on day one? Nah. And so far, so good.

FWIW from a non-MINI perspective: I switched a 1995 Subaru 4EAT automatic transmission from non-syn to Redline at 71K miles and it didn't break a sweat. Still kicking at 352K+ miles.

 

My 2017 Starts in first. It won't downshift to first unless I come to a complete stop, then stays in second.

 

Mine sure sounds like it starts in second, because if I don't give it more than maybe 50% throttle off the line from a stop, it doesn't accelerate as hard as if I stomp it. I can also feel a downshift if I roll in easy the first couple feet than stab it. This is in regular "D". If I move the shifter to the left into "sport" or whatever, it then starts in first. Maybe they changed something for 2018? Or maybe I am not feeling what I think I am.

 

Mine does the same as @TVPostSound , if at a stop in D it will begin takeoff in 1st gear. I can tell because if, at a stop, I shift it to S it goes to S1 or if I put it in M1 it feels the same as taking off from D.

HOWEVER, this was not consistent until I did a trans fluid drain/refill (approx 50% drain, you can't get it all out with a simple drain as discussed elsewhere) at about 101K miles (note I bought the car at around 72K miles, so my observation set is limited).

@renchjeep I think my 2017 was behaving more like yours until the fluid change.

 

Odd. Ever since I bought mine used with 21k miles, I can feel a distinct downshift when stopped and idling in regular "drive" and moving the lever left into "sport". I can also feel it when going from "sport" back into regular "drive", but it's not as distinct. Also, the RPM changes when I do this. It increases RPM when going from "drive" to "sport" and decreases when going from "sport" to "drive", which says to me the transmission is doing something.

 

Regarding the behavior when moving the lever to either side, what you describe sounds like mine before and after my fluid drain/refill. It also sounds like what my movement of the lever does whether I am stopped or not -- I have made the same observation at highway speeds and lower. The RPM uptick when moving the lever from "drive" to the M/S position is consistent with a downshift, and the RPM drop when moving the lever from the M/S position to "drive" is consistent with an upshift. On my 2017 I have been pretty clear for a while that this downshift when kicking over to M/S and upshift when kicking back to "drive" is exactly what is going on.

The main differences I noted after the fluid drain/refill were the car being generally peppier and more prone to downshift on its own to maintain acceleration and speed (most perceptible -- WAY perceptible -- in Green/ECO mode), and the pretty obvious shifting all the way down to 1st gear when stopped (noticeable because takeoff is very different from 1st than from 2nd).

My take on all this is that it isn't so much an either/or thing with the automatic transmission in the F56S -- it's nuanced, and to the extent there is a loss of responsiveness over time (presumably due to needing a fluid change that BMW says isn't necessary), that loss of responsiveness is pretty gradual, to the point that it would not be noted if not paying deliberate attention. Again, I was extremely surprised by the change/improvement in behavior of mine post-change -- I figured I was just doing smart "unnecessary" maintenance at 101K, and it turned out the prior lack of that "unneccsary" maintenance had real (reversible) consequences. Who knew?

 

Interesting that MINI considers the fluid lifetime since they changed the recommendation from lifetime in the previous generations (at least for the 1st). I guess it’s probably all of the BS of planned obsolescence, marketing of lower maintenance and costs, hoping people buy a new car before there’s an issue.

 

No direct experience but in talking with service techs -- not MINI techs but another German car brand -- their recommendation is to change the transmission fluid *early*. At around 1/2 the called for miles. For example if the factory calls for a transmission service at 90K miles have it done at 45K miles.

A fluid service removes the old fluid which is laden with particulate matter. Sure very fine being able to pass through the filter. But its presence can change the viscosity characteristic of the fluid. The transmission fluid filter is replaced which can only improve oil filtering and flow.

But I have my doubts about the transmission becoming accustomed to the different viscosity.

More likely with big miles the transmission valve body suffers wear. This is a very precision piece of hardware that is very sensitive to wear. The "thicker" fluid compensates for this to some extent. A fluid change of course results in a thinner fluid but with wear the transmission just ain't the same.

With an early fluid service the wear is avoided.