Had the same issue on my 05 4.4 at around 58-60K miles. Had issues recreating the problem with the tech, but they did note it. It got worse and finally the tech was able to feel it. Dealer replaced tranny under good will. Phew that would have cost a lot out of warranty.

^, if I could only make this happen! was the car CPO or did you have an aftermarket warranty?

I got lucky... car is not CPO and no warranty. I complained about it for about 1 year and finally the tech was able to recreate the issue. Decent folks here at Schomp BMW in Denver. They did tell me this was the last good will they will do for me, of course it was a big one. It's the way you go about it to get them to take care of things outside of warranty.

Late entry to this thread, but here's a couple ideas and some things to try.

From the sound of it in the OP it could be either the torque converter circuit or even possibly the transfer case.

Some quick things to try...
If it is in the transfer case you can simply unplug the VTG motor on the case to prevent it operating the internal clutch pack. This will cause the 4x4 and DSC warning lights to come on, but that is just part of diagnosing.

Since it seems to do it under certain circumstances/speeds while driving, get it doing it then shift into sport mode. This changes the speed and parameters for the torque converter lockup clutch operation. If it stops doing it at that speed and you gotta drive faster to get to the same feel then you confirmed that it is in the TC lockup circuit, which is usually cured with the mechatronics replacement. (mechatronics = transmission control module built on to the valve body on 04 and up V8 X5s)

Will this same trick work for my 2002?

You don't have clutch plates in your transfer case (pre x-drive)

Oh, good. One less thing it could be.

Thanks weasel for all the info. I'll give it a shot.

@ dinan e39
does the problem happen only with the A/C on
I have experienced the same old same old on every BMW I have driven
3 , 5 , X3 , X5 , series in various guises , the 3 and 5 `s were new with a few hundred miles on the clock .
diesel or petrol , same old same old .
I reckon it`s a computer blip of sorts .
I don`t let it bother me
if it becomes a problem I shall look to repair it .
my old E38 does it sometimes . it does the lurch sometimes , has been doing stuff for 30,000 miles now and then .
most of the time it`s fine .

Macman,

Thanks for the confidence. These cars are completely governed by computers these days and it would not surprise me if it's exactly what you are describing.