Haven't posted in a long time, but thought this was worth sharing. A short story:

Bought my 2006 X5 3.0i 8 years ago with 143,000 miles. Shortly after purchase, I changed the transmission filter / fluid (BMW) and transfer case fluid (BMW). I didn't reset the transfer case calibration because I only had INPA and dealer wanted $300+.

Fast forward to last week. I hit 243,000+ (100k since last change) and decided to change the fluids again. I changed the transmission filter / fluid (Valvoline Dexron VI this time - bought 3 gallons under $60 for 2 rounds) and transfer case fluid (BMW). I finally got ISTA Rheingold to work and reset the transfer case calibration. Aside tip for ISTA I wish I'd seen sooner: be sure to unpack and copy all language files (not just English) and change baud/latency on COM port.

Anyhow, the difference is noticeable. It just feels "stronger", shifts smoother, and no more occasional hesitation. I can honestly say in the 100,000+ miles I've owned this car, it's never driven better.

I don't know if it's just the transfer case reset, the fluid changes, the "upgrade" to Dexron VI, or all of the above, but I highly recommend a refresh/reset for those that have put it off.

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Silver 2006 BMW X5 3.0i Auto