[Phiwee]

Recently when I tried to do a pull on the freeway entrance ramp, I noticed the car did a very hard “bog” like if the transmission slipped and didn’t know what to do.
Didn’t experience it for a while after that. Now it happens all the time even on slow normal day to day accelerating, feel it more on higher gears, where whole car is pulsating, feels like it’s coming from around area of driver seat.

Your help would be Much appreciated!

[alex0607]

Have it checked by a mechanic on a lift.

[95blkmax]

You haven't even said what kind of car you have (your details under your user name say F30), what year, mileage, any transmission service history, if it's x-drive/ RWD, from what gear to what gear this happens, if in normal/ sport/ eco mode, if you have any trouble codes present (which you should), etc...

So it's kind of difficult to offer assistance without proper details of the situation.

[ultraboosted]

I had the same scenario getting on the highway. Went to accelerate to merge, and boom, drivetrain malfunction and limped home. Turned car off, and started it back up no issue, but it would come back any time there was any kind of acceleration. my giubo (flex disc) and differential bushings were shot. replaced those, and motor mounts after realizing it wasnt a drivetrain malfunction like the warning displayed. seems to have done the trick

[DementedF10]

I had recently bought a higher mileage 535ix and noticed something similar to what you are describing. I first thought it was a miss or a boost leak but after more and more driving i feel it is in the transmission. So this past weekend I did a filter and fluid replacement on the trans and the first drive instantly felt perfect! a few 100 miles later and what I suspect is the fluid from the torque converter mixing with the new fluid, i have a very slight "hiccup" when accelerating. My plan is to do 2-3 more fluid drain and fills and see if that helps. Im pretty sure the 140,000mi on the fluid did not do it well.