tranny stumbles every 2-3 seconds when cruising

[X5_Rob]

it doesn't happen every time I go for a drive but its happening more frequently... when cruising 40/50/60+ mph the car will hiccup or stumple for a moment and then continue... happens in a split second... and is consistently every 2-3 seconds or so when its happening.. I can drive for 30 minutes and it will happen the whole time... next time out no problems... I get a sense its drive train related but who knows... any thoughts out there?

I have a 2005 4.4 with 85k miles...

Thanks!

[Big "J"]

Is it more noticeable under acceleration? Mine started stuttering or hesitating more during acceleration and I believe my torque converter is giving out. I'm going to change the tranny fluid & filter in the next day or so and see if that will help prolong the inevitable or cause me to nose dive.

[IanP]

Maybe try searching for torque convertor lockup?

[TiAgX5]

If the RPMs go up during hesitation it might be the TC, If RPMs drop it's not.

[PCS X5]

I just had the same or similar symptoms happen to mine. It was most prevalent at 35-40 mph, cruising. Hiccup is a very good description. The issue showed up a few weeks ago so I brought it in to the dealer immediately as our 3rd party warranty is about to expire. They were able to replicate the problem and the diagnosis was that the torque converter was failing. Torque converter was replaced but a few days later the hiccups started again, although this time a bit more subtle. The car is back in the shop now about to get a new transmission.

I spent a bit of time last night on this site looking for a similar problem, but to no avail. I did find lots of threads regarding transmission problems and some with torque converter issues too. From what I gather, a failing torque converter that is not quickly addressed/fixed will wreak havoc on the transmission eventually.

I suggest you get it looked at ASAP in hopes of minimizing repair costs. Of course we all know that "minimizing", "repair costs" and "BMW" do not exist in the same sentence in this world.

Good luck!

BTW, I'm just over 60K miles, '05 4.4i.

[X5_Rob]

Thanks so much for the feedback... I suspect its either the TC or combo of it and tranny... tranny has had some odd incidents of late, pausing to slip into gear and then slamming into gear from a dead stop (scaring all passengers of the car to death) and a very occasional major hiccup when cruising which also has a loud noise and shudders the car....

Whatever it is it certainly sounds expensive...

[hippee0]

any update on this guys mine is starting to slam into gear sometimes from a dead stop

[texmln]

While it very well may be the transmission causing your problem, a bad oil separator can cause your engine to stumble in a way similar to your description. 85k is in the neighborhood of oil separator problems too. Bad trannys and torque converters are more rare at this mileage. Any codes?

[bbultman]

If the stumble/hiccup goes away when driving in Sport mode or when in cruise control, it's the TC. Sport mode increases the TC lock up solenoid pressure so it doesn't lock/unlock every 2-3 seconds. Cruise control sends an input to the trans ECU to keep the TC locked up as much as possible so the trans isn't shifting constantly with variations in the road - hills, etc. Good simple test. Mine has been doing this for 10k miles now. I just drive in Sport mode and all is fine. However, the inevitable trans rebuild is looming. If you have banging shifts, bad shudders at certain speeds, etc, you probably need to get the trans done sooner than later. Good luck.

[X5_Rob]

I brought it to a very reputable BMW repair shop. They determined my alternator was producing voltage spikes and error codes.... apparently the transmission electronics did not like these voltage irregularities... they believe the torque converter and tranny are fine... .replaced the alternator and all seems well.. I'll update in a few days/weeks when I get some miles driven on it... As odd as it seems the alternator repair seems to have solved my issue...