[g911turbo]

I've done some searching but cannot find anyone else with this issue. Recently my GF bought an e83 2008 X3 (auto), still under CPO, but before I just take it into the dealer I wanted to potentially arm myself with a little knowledge.

Car drives fine normally, and is very smooth all the way up to 80+ MPH. The one thing I've noticed however, is that when letting off the gas, the car seems to "engine brake" a substantial amount more than my e90. Almost as if the transmission is holding it back. I just attributed this to software (and yes it is the newest SW, programmed when we just had the lifters replaced about 2 weeks ago).

The problem arose when I used her X3 to haul 4 people + driver (me) + luggage to and from customer appointments. Under this weight load, when doing the same coasting at highway speeds, I noticed and felt a substantial vibration in the car. Even the slightest depression of the accelerator to maintain speed (or accelerate) would cause the vibration to disappear completely. I could even decelerate with my foot still slightly touching the gas, and no vibration. Only when I completely let the car coast, at highway speed, did I experience this vibration.

I did not notice the vibration when coasting at low speed (30 or lower), somewhat noticed it when coasting between 30-50, and easily felt/noticed it 50+ when coasting.

THIS VIBRATION ALL WENT AWAY once I dropped everyone off at the airport and it was just me in the car. The car still feels like its engine braking too much (even in 6th), but no more vibration.

I don't think it's wheels / tires based on the symptoms. I'm wondering if it's something drive train related. Any words of wisdom would be appreciated. I plan to crawl under the car soon, once it's no longer 0 degrees F here.