Alternative Transmission Fluid for 1999 528i, automatic ???

That 'success' is almost impossible to prove, unless the transmission successfully completes another 100,000 miles.

My view too unless the fluid is identical to original spec - or you've researched one which works as well but has to be changed at more 'normal' intervals. Because if the gearbox fails due to the wrong make fluid you'll have no comeback on anyone.

According to my Bentley Manual for my 3 Series, the automatic transmission is filled with Dexron III, "but the factory might have used alternative fluids."

I would not hesitate to use Dexron III in my transmission. The only consideration is the possibility that your 5 Series uses a different transmission than the 3 Series from the same vintage.

I recently had a fluid flush in a different car that uses Dexron III, and the cost was $70 (USD). The shop disconnected the transmission cooling lines at the radiator, and pumped new fluid in that pushed the old fluid out at the same time. You might consider dropping the bottom cover and replacing some of the filters and such that may need attention from time to time, but in my instance I am the original owner of the car in question so I opted for the basic service. In any case, the service you are looking for should be available for well under $150.

Agree, one problem with slush boxes is you can't ever drain out all of the fluid. Unless you actually pull the tranny, there will be fluid stuck in places like the torque converter. Find out what fluid your car comes with and replace with the exact same thing.

Personally, I'm glad I got a manual tranny on my 90 535i with 107K miles, I change it every 30K or so with a good synthetic like Redline or Royal Purple and its cheap and easy to do!

Some say you can do a power flush by removing a pipe to the cooler with the engine running while filling with fresh and do so until it runs clean. This should change the fluid in the TC too.

Uh, there's no drain plug on the torque convertor? You sure?

I had the same requirement for my 1999 E36 323i auto. I asked a major transmission repairers/remanufacturers who do many, many ZF boxes each year, and they said they use DexronIII in these boxes, but if I specifically wanted the Esso LT71141 fluid they would get some in. complete fluid change and filter/gaskets runs to about £125inclusive. Not on your side of the pond I know, but

Certain. ;-)

And even if there was there's no way to get rid of contaminated fluid after a 'box failure which is why it's usual to replace the TC at overhaul time.

Wow. Is there a good reason for that? I'm used to being able to drain the convertor, too.

I'd guess you'd have to wouldn't you?

I've never seen a drain plug on a car TC - and I've had autos since the '60s. But not a US one.

All Mercedes have them.

A "power flush" might work, that's what Toyota recommends for its auto trannies.

But I haven't heard that mentioned as a sure fix-all for BMWs. Further, with some BMWs, especially newer ones, requiring really expensive "lifetime" fluids, it becomes a question of how much fluids are required. Then again, I guess its worth the expense if the alternative is your tranny going out at 100K or less, ouch!