Hi all, I am brand new to this forum and new to the Bimmer world. I just purchased my first BMW (back in Oct 11). I have the same exact problem, although mine is 530i E60...when I did the scan the fault code that it showed:

P17e9

Any help?

I wanted to follow up on the posts on the X5 4.8is Transmission slipping / noise between 4th and 5th gear. (code 4F8A)After driving around for 9 months with the problem and babying the car through the shift it is now happening just about every time now even with the babying. Went back to my local BMW independent mechanic this month and they are still guessing what the problem is and leaning towards pulling the transmission. Wondering if anyone out there has come up with a solution. Appreciate your help !

This thread has been untouched for awhile - unfortunately I am having the exact same problem at 59K miles on my 2006 4.8is. Dealer says replace the whole thing; will not rebuild. My indie says the same thing; will not rebuild. Dealer first quoted $9200 repair or $5000 for a trade-in. Both ridiculous. He came down a bit to $5700 with a 2-year warranty. Why is their premier, high performance tranny failing at <60K miles? I am second owner and drive it pretty mildly. I don't know what the first owner did with their 23K miles. Can't even try to unload it somewhere because you never know if this slip will show up on the test drive or not. Like these fellas, I'm in a jam. Dump it and lose a fortune, or spend a fortune and wait for the next thing to break? This 4.8 is a great car when it's working, but seems like it's always broken. Even if I fix the tranny, I have an air suspension stuck in transport mode (and perplexing the dealer) and the infuriating front PDC failure that ain't cheap unless I do it. How can I praise the car and whine about it at the same time? I wonder that myself. I must be insane. Not sure what I'm going to do. I still have a couple of days before I need to make a decision.

Slipping and codes coming up 4F8A
 

I was having all the same problems as the above posts and I found the solution for my 2005 4.8is. I noticed that I was getting the slipping noise more often when I had 4 people on board, so more weight. Took a close look at my suspension and noticed the inside wear was real bad on both of my rear tires. Had 4 wheel alignment done on the car along with all new tires and that was the end of the codes coming up and the slipping sound. Happy it worked for me as the suggestions on a new or rebuilt transmission were all i was getting from the BMW mechanics.

Wow, poor rear wheel alignment with a heavy load causing slipped shifts and creating codes in the transmission. Good to know no matter how crazy it seems. Unfortunately I get this with just me and I checked my tires; all wear seems nominal 21 months into this set. If anyone else has had this fix, or can suggest others, please chime in. I have spent days reading the old threads here and the insight is valuable. Thank you.

More and more gearshift issues with the 6HP26 seem to be related to faults with the Mechatronic solenoids. I would recommend swapping the solenoids around (like-for-like colours only, obviously) and seeing if the problem transfers to a different shift. Clearly this will upset the adaptions temporarily but it should show if this is where the problem lies. New solenoids can be purchased individually.

Phil

Yup, I agree. I swapped all of mine out, and its like having a new transmission.

My car started to slip around 1 month ago after replacing the sealing sleeve of Mechatronic and added 2 liter of transmission fluid at dealer. However, the slip does not come all the time, only when I was trying to speed up sometime. Before having warning text of 'trans. fail save mode' in the cluster, a very weird sound and hesitation to kick down appears. Now, everytime I hear the sound and feel the hesitation, I just leave off the gas pedal immidiately to stop accelerating and press it again, everything returns to normal without having warning, but if I keep stepping on the gas pedal, the warning sound with the text will come and the system goes into safe mode. If the warning comes, I switch off the engine and start it again, everything returns fine. It also works fine when in manual mode. In my case, what the problem could be? Do I need to have the transmission rebuilt or what? Thanks for help! Here is the diagnosis result.