42, The meaning of life
Join Date: Jul 2009
Location: Melbourne, Australia
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Welcome to the Werkz
I have a (10/1999 Build) 2000 740iL which had some quirky issues when I purchased it. By quirky I mean it would drop and recover 80 - 150 RPM when under light load at 50 - 70km/h. After changing a variety of things I put the car in for a transmission service at a specialist transmission shop (Fluidrive Australia). I explained the issue to them and they ran a set of diagnostics on the transmission after changing the filter and fluid, nothing to report, they suspected engine management issues. After I collected the car, I noticed within 4 - 5 km that the drop and recover issue was gone, and the gear shifts were smoother as well.
BMW will tell you that its a sealed for life transmission, but I called ZF (manufacturer of gearbox) and spoke with them about this "Sealed For Life" policy, and they pointed out that BMW also supplies the replacement gearboxes. ZF's recommendation is that the oil and filter should be changed every 40,000 - 60,000 miles depending on driving conditions. In the end its up to you who you choose to run with, but for me replacing the lifeblood of a gearbox makes sense, because I have a car to drive, not to push.
If you choose to change the oil, choose a reputable workshop that can pump the old oil out of the Torque converter as well the gear box oil pan, and use the genuine BMW oil filter because some of the 3rd party products can collapse and restrict the oil flow (bad).
If they will let you, get a look (and smell) of the old filter internals, I'd almost put money on the oil be black as black can be, and as rancid and spent as you care to imagine.
Good luck, hopefully there are no large chunks of metal amongst the sludge that used to be your transmission fluid.
Riding in style