I did the drain and refil method on mine around 135k and am at 145k now. No troubles.

I have a personal belief that some of the bad experiences are from "power flush" using generic ATF. If the "flush" is less than $500, you know they aren't putting 15-20 liters of the right fluid through it.

His post may be well written but it lacks any statistical data to support the conclusion changing the transmission fluid can lead to failure of the transmission. Until such data can be provided it is nothing more than an urban myth.

Could that myth have been started by someone working at BMW? :yikes:

Been almost a year, mine is going fine.

It's a possibility. One I'm not in a position to say one way or the other.

The service and warranty booklet for my 2006 4.4i, on page 3 if you want to check me, says pretty clearly "Automatic Transmission Service: Change ATF every 100,000 miles." Does not say "lifetime". Does not say "flush".

So I did that - drain and change at 100k. At 140k now. No issues caused, smoother after change. Will do again, maybe at 150 or 160.

If reusing the original fluid, I would still run it through a fine mesh filter such as one for paint finishes, before pumping it back in to make sure there wasn't any loose debris in it. The important point is that you're not altering the "chemical" operating environment the friction components are accustomed to.

2002 X5 274,040 miles
2004 325i 118,500 miles

While not disputing some of the claims made here, I do find it interesting (some might say amusing) that other complex hydraulic mechanisms (in such things as excavators, hydrostatic drive units) have no such claims to "lifetime fluid". Our excavators - we would NEVER dream of running the hydraulic drive oil for more than a few hundred hours at most. Our large mowers - same thing. The hydraulic fluid is lifeblood to these machines, and we're not talking a few grand worth of transmission - we're talking tens of thousands of dollars worth of repairs if you have a hydraulic issue that contaminates the system.

I suppose though, since the X5 really is aimed at the general consumer market, they (BMW) can make the assumption that for the vast majority of purchasers there will never be an issue in the "lifetime" (ie economical repair life) of the vehicle, so the claim can be argued as valid.

Number one enemy of hydraulic fluid is heat, number two is dirt. Heavy equipment is far more likely to encounter those issues than a vehicle transmission with a small vent tube. Likewise, operating pressures of those systems are typically much higher than in a transmission, so any contaminants would be more likely to damage seals and sliding surfaces... which is why I do however, regularly change power steering fluid.

If I had arranged for shop performed flush & fills every 50,000 miles on my transmission as some other members do, I probably would have spent between $2000 and $2500 on that maintenance by now, and still have a unit with 274,000 miles of wear on it. Depending on whether or not it ever fails, a re-manufactured unit with a 3 year warranty and all new wear components can be installed for about $3000. I just think that's the more cost effective and less time consuming way to go. I guess we'll see as I continue to rack up 500 miles per week!

2002 X5 3.0 274,040 miles
2004 325i 118,500 miles

The ZF repair manual for the 5hp24 is at the link below. It effectively defines Lifetime as 10 years.

I read this to mean the fluid must be replaced every 10 years and there is no restriction on replacing it earlier. I am surprised they don't use a mileage criteria as well.

http://www.jagrepair.com/images/Auto...r%20Manual.pdf