Odd Steptronic Downshift Problem - Any ideas?

[Cabrio330]

Coasting downhill at say 50 mph and maybe 2k rpm, approaching a corner so I lightly step on the brakes, the transmission abruptly downshifts which causes engine speed to jump instantly to say 4k rpm, which results in a ton of engine braking. No real pattern as to what speed I am coasting at, it happens at almost any speed. This happens in normal steptronic mode, although I haven't tried to replicate the problem in Sport or Manual modes. I have owned a 2002 330cic and a 2005 545i both with Steptronic and put in about 100,000 miles betweent thos two, and have not experienced this problem. If you were riding in the car with me, you would respond "WTF?!" It is that noticeable!

Then, as I get back on the accelerator (normal, not hard) after entering the corner, it seems to take longer than normal for the car to upshift to the gear I would expect at that MPH and RPM.

Any idea of causes? I know that BMW claims the transmission fluid is lifetime, but I don’t believe that!

Thanks in advance!

[danewilson77]

First thing. Lifetime fluid = 100k miles, as defined by BMW, after the fact.

Second thing. Change fluid, filter, magnets, gasket, and bolt, with kits available on line.

Third thing. Welcome

HTC Thunderbolt+TT

[mikeyb74]

Fluid and filter change and see what happens.

[johnrando]

I get that heavy downshift enginge braking thing too,, 50K miles on my car. I don't recall the 2nd half of your issue, taking longer to downshift. Keep us posted on the transmission maintenance and how it works. And, welcome too.

[ryankokesh]

That's not the same problem I had; mine kinda jerked downshifiting from 2nd to first. I took it to my indy though and he upgraded my transmission software and it's been smooth sailing ever since (at 117k now). Not sure if that'll help, but I find that a lot of people don't know that's even an option. Personally, I had no idea the transmission even had software.

[Cabrio330]

Thanks for the suggestions. My thought was to do as advised - change the fluid, filter, clean the magnet, etc. I was hoping that someone here had experienced these symptoms and could confirm that this maintenance regime solved their problem. I will post this on that other E46 forum only because it may get more views, but I started here because of the civility of this forum. Glad to be a member and grateful I made it in before the cut-off!

By the way, this is my 4th E46 car, so you can tell I love the model. First was a 2002 330cic, then a 2003 330i ZHP 6-speed, (E46 streak interrupted by a sweet 2005 545i), then a 2002 M3 convertible 6-speed, and now this 2004 330i ZHP steptronic. I have also owned a 1997 328ic, an E28 M5, and currently also own a 1991 325ic and a 1972 3.0CS Coupe. All of these have had pros and cons, but the 2003 ZHP 6-speed has been my overall favorite car. But then again, everyone here already knows that!

[Cabrio330]

I get that heavy downshift enginge braking thing too,, 50K miles on my car. I don't recall the 2nd half of your issue, taking longer to downshift. Keep us posted on the transmission maintenance and how it works. And, welcome too.

John, your reply made me re-read my original post - I incorrectly said "downshift" in the second paragraph, but I just edited it to "upshift."

[johnrando]

John, your reply made me re-read my original post - I incorrectly said "downshift" in the second paragraph, but I just edited it to "upshift."

Ah, I'll keep a look out for that on mine.