[BeastMode335i]

2013 - F30 - 335i - 8AT - 125k miles

I was driving around the other day and noticed on one of my downshifts, when I went from 4th to 3rd @ around 40mph the RPM's dropped a bit then bounced back up, and then did the same thing when I downshifted from 3rd to 2nd, with my foot off the gas the entire time. It did this a few more times, but not every single time, and then after I parked and went to grab lunch, I came back out to my car starting up just fine, but refusing to go in to reverse, neutral, and drive. Every time I'd try, it would automatically get thrown back to park. I tried the electronic force neutral by holding the shifter one click forward, no luck. I manually screwed in that bolt on the trans to get it on a tow truck and I got it home in my driveway now. I'm just throwing one single code in MHD.

- Transmission Active Codes -
420641 - Parking lock defectively engaged: plausibility, driver's demand/sensor feedback.

Seems like this question has been asked a few times over the years, but nobody has seemed to report a solid fix. Some say it's low fluid, some say mechatronic, but I figured if it was mechatronic related, it'd throw a code relating to that, right?

I ordered a new pan/filter and also some trans fluid, so I'll try that first but just figured I'd post to get some assurance, in case anyone else experienced this. Wondering if I should drop the mechatronic and replace the bridge seal as well, kind of on the fence about that, as I only have jack stands.

[BeastMode335i]

Ok so just dropped the transmission filter/pan and yeah, somethings not right. The fluid coming out looks like chocolate milk...

I had a failed oil/heat exchanger a few months ago and my coolant system got contaminated with engine oil, but I fixed that. I also replaced a lot of the coolant lines, the overflow reservoir, water pump, thermostat, and radiator. Any chance this is from that?

Fix wise, do I just need to fill and flush my transmission a few times to get this milky liquid fully out of there?

Thanks!

Update: Removed one of the cooler lines going from the transmission to the heat exchanger/trans cooler, and that same fluid came out of there, guess I found my failure.

[BeastMode335i]

What I'm dealing with.

Hopefully I can find someone local that can safely flush this out.

[AmuroRay]

Wow! I wish you the best on figuring this out man.

[BeastMode335i]

Originally Posted by AmuroRay

Wow! I wish you the best on figuring this out man.

Thank you brother I appreciate it!

Just hoping that a few flushes will take care of this. ::fingerscrossed::

[BeastMode335i]

Swapped in a known working mechatronics today, and just as luck would have it, the issue is still there and my car still won't shift in to any gears.

Anyone have any advice on troubleshooting a parking lock, since that's what the code is for?

[LA1Z24]

I'm going to take a guess that your oil to coolant transmission cooler has failed, filling the trans with coolant, which in turn smoked the clutch packs.

[BeastMode335i]

Originally Posted by LA1Z24

I'm going to take a guess that your oil to coolant transmission cooler has failed, filling the trans with coolant, which in turn smoked the clutch packs.

The trans cooler did fail, and was fixed, and I'm still just throwing that one single code for parking lock engaged. Wouldn't I be getting ratio codes if the clutches were bad? Or slipping gears and stuff of that nature?

[BeastMode335i]

So after new pan filter/fluid, mechatronics unit (valve body + EGS), coding in the new unit, fully resetting TCM adaptations, etc... It's still doing the same thing.

Anyone have experience with the parking pawl on these cars? I'm going to inspect that but not 100% what to look for.

[LA1Z24]

As I've said in your other thread, and on reddit...You need a new transmission. Coolant in the trans fluid ruins the clutch packs and the oil pump. One more time, you need A COMPLETE NEW TRANSMISSION. The park pawl operates off fluid pressure. Coolant does not lubricate. An oil pump needs lubrication. Running coolant through the pump ruins it. For all the money you've spent throwing parts at it, you could've replaced the transmission with a used unit.

[AmuroRay]

Good news, transmissions are pretty cheap::


"sport" transmission:
https://www.car-part.com/cgi-bin/search.cgi?userSearch=int&userPID=1000&userLocatio n=All+States&userIMS=&userInterchange=C%3FD%3F%3F} }}}}HO&userSide=&userDate=2015&userDate2=2015&dbMo del=9.63.1.1&userModel=BMW%20435i&dbPart=400.1&use rPart=Transmission&sessionID=13000000785003485&sUR L=www.car-part.com&userPreference=price&userZip=34112&userLa t=27.8042000&userLong=-82.2864000&userIntSelect=339772&userInterchangeSou rce=HO&userUID=0&userBroker=&iKey=&userPage=16

Non sport:

https://www.car-part.com/cgi-bin/search.cgi?userSearch=int&userPID=1000&userLocatio n=All+States&userIMS=&userInterchange=C%3FEB%40}}} }}HO&userSide=&userDate=2015&userDate2=2015&dbMode l=9.63.1.1&userModel=BMW%20435i&dbPart=400.1&userP art=Transmission&sessionID=13000000785005804&sURL= www.car-part.com&userPreference=price&userZip=34112&userLa t=26.1178000&userLong=-81.7361000&userIntSelect=339778&userInterchangeSou rce=HO&userUID=0&userBroker=&iKey=&userPage=4

I don't know the difference because I'm a manual.

[BeastMode335i]

Originally Posted by LA1Z24

As I've said in your other thread, and on reddit...You need a new transmission. Coolant in the trans fluid ruins the clutch packs and the oil pump. One more time, you need A COMPLETE NEW TRANSMISSION. The park pawl operates off fluid pressure. Coolant does not lubricate. An oil pump needs lubrication. Running coolant through the pump ruins it. For all the money you've spent throwing parts at it, you could've replaced the transmission with a used unit.

I appreciate your feedback, it sounds like you didn't see my response/question though. It was in regards to not throwing any codes related to the clutch packs, and the likelihood of them still being bad. I researched a bit of what you had mentioned there, and it seemed that the general consensus was that if my clutch packs were fried, I'd throw a code relating to them, and I'm not throwing any codes but one as it relates to the parking lock. Not saying my trans isn't fckd, just want to make sure I don't jump the gun on something that can be fixed. If it can't be fixed, I have no problem swapping it out, but again I'm just trying to make sure I check all the boxes.

[BeastMode335i]

Originally Posted by AmuroRay

Good news, transmissions are pretty cheap::


"sport" transmission:
https://www.car-part.com/cgi-bin/search.cgi?userSearch=int&userPID=1000&userLocatio n=All+States&userIMS=&userInterchange=C%3FD%3F%3F} }}}}HO&userSide=&userDate=2015&userDate2=2015&dbMo del=9.63.1.1&userModel=BMW%20435i&dbPart=400.1&use rPart=Transmission&sessionID=13000000785003485&sUR L=www.car-part.com&userPreference=price&userZip=34112&userLa t=27.8042000&userLong=-82.2864000&userIntSelect=339772&userInterchangeSou rce=HO&userUID=0&userBroker=&iKey=&userPage=16

Non sport:

https://www.car-part.com/cgi-bin/search.cgi?userSearch=int&userPID=1000&userLocatio n=All+States&userIMS=&userInterchange=C%3FEB%40}}} }}HO&userSide=&userDate=2015&userDate2=2015&dbMode l=9.63.1.1&userModel=BMW%20435i&dbPart=400.1&userP art=Transmission&sessionID=13000000785005804&sURL= www.car-part.com&userPreference=price&userZip=34112&userLa t=26.1178000&userLong=-81.7361000&userIntSelect=339778&userInterchangeSou rce=HO&userUID=0&userBroker=&iKey=&userPage=4

I don't know the difference because I'm a manual.

Thanks brother, much appreciated! I do have the sport trans, I believe the diference is in the torque converter. At least that's what I've read thus far.

I have thought about manual swapping, but it'd probably be easier to just swap in an 8HP70 and up the boost a bit. =)

[AmuroRay]

Originally Posted by BeastMode335i

Thanks brother, much appreciated! I do have the sport trans, I believe the diference is in the torque converter. At least that's what I've read thus far.

I have thought about manual swapping, but it'd probably be easier to just swap in an 8HP70 and up the boost a bit. =)

I got you bro

[BeastMode335i]

Just wanted to update the post, swapped in a replacement transmission today and my car is back on the road! I think a bit of ATF got in to my coolant when the transmission heat exchanger failed though. Otw home from the mechanic shop from picking up my car, it said low coolant and when I checked it out there seemed to be a bit of oil in the expansion tank. Guess the fun hasn't stopped just yet lol. At least my transmission is fixed though! =)