[Koolsilver]

So I've had my transmission flashed with the Alpina B3 flash for about a month now and I've started to notice it acting what seems weird to me and I just wanted to see if anyone has similar experiences or maybe it's normal. My car is an 09 e90 335i obviously AT. What I've noticed is some gears I think mostly shifting into 4th and 5th the car will shift to that gear but the RPM will not drop as much as it should and kind of hold that RPM while still accelerating and then drop a bit more a few seconds later. It's almost like it's slipping but the RPM stays constant and I'm gaining speed still it's honestly really like a CVT transmission. I'm not sure if this is normal or not. I'm a bit scared because to me it seems almost like it may not be fully engaging that gear for a second which may cause extra wear but I don't know enough about auto transmission to say anything. In M and S mode this doesn't happen at all the transmission shifts fast and hard.

[seanblee]

Sounds more like the torque converter lockup clutch isn't engaging as quickly with the Alpina flash. I think mine behaved in the same way when I was running the Alpina tune, but I removed it a while back before taking the car to the dealer and I haven't bothered flashing it back again...

[ferocity02]

Maybe because it shifts at a lower RPM you are noticing the converter slip a lot more.

[Jeff@TopGearSolutions]

It's probably normal, as others said, torque converter hasn't full locked.

If you are going to drive aggressively, it's best to drive in Sport or Manual mode with the Alpina Flash.

D mode tends to lug the engine and is for conservative throttle only.

Alpina with the right tune can be so smooth in D mode you can barely feel the shifts and go all the way to 6th gear by 40 MPH.

[zmon1300]

Originally Posted by Koolsilver

So I've had my transmission flashed with the Alpina B3 flash for about a month now and I've started to notice it acting what seems weird to me and I just wanted to see if anyone has similar experiences or maybe it's normal. My car is an 09 e90 335i obviously AT. What I've noticed is some gears I think mostly shifting into 4th and 5th the car will shift to that gear but the RPM will not drop as much as it should and kind of hold that RPM while still accelerating and then drop a bit more a few seconds later. It's almost like it's slipping but the RPM stays constant and I'm gaining speed still it's honestly really like a CVT transmission. I'm not sure if this is normal or not. I'm a bit scared because to me it seems almost like it may not be fully engaging that gear for a second which may cause extra wear but I don't know enough about auto transmission to say anything. In M and S mode this doesn't happen at all the transmission shifts fast and hard.

I have that issue sometimes too. Usually happens when the car is cold. I usually just drive conservative until car is warmed up, then just switch over to M mode or S mode ( if you want the car to shift by itself ) and carry on.

[Koolsilver]

Thanks for all the response I'll try to record a video of it to give everyone a better idea. I would say I'm an above average DIY mechanic but I have no knowledge on auto transmissions. I have no idea how a torque converter works or if it's bad if it's not fully engaging or any of that.

[seanblee]

Originally Posted by Koolsilver

I have no idea how a torque converter works or if it's bad if it's not fully engaging or any of that.

HowStuffWorks has a decent explanation of how the torque converter functions, including what the lockup clutch does. It's there to improve efficiency by locking the two halves of the TC together, eliminating the energy losses it would otherwise cause. It sounds like your transmission is working normally, so I wouldn't worry about it

[Jeff@TopGearSolutions]

Originally Posted by Koolsilver

Thanks for all the response I'll try to record a video of it to give everyone a better idea. I would say I'm an above average DIY mechanic but I have no knowledge on auto transmissions. I have no idea how a torque converter works or if it's bad if it's not fully engaging or any of that.

Torque converters are allowed to slip. It allows for smoother shifting.

They should lock in M mode and sport mode though. That in essence means it's sending all the power.

Definitely check out some reading material on them if you are interested.

Auto slush boxes always allow for some slip time. Not only is there a slip time but slip amount and all that can change depending on load and RPM. Auto transmissions are quite complex not only in the inner workings but on the tuning side of things.