[tetsuo111]

I have a little unusual track setup due to being limited to one car: 2011 E91 328i xDrive sports wagon. The car serves dual purpose as a daily driver and I track the car a half dozen times / season. I'm an intermediate driver, with aspirations to continue improving my driving proficiency. The car has been modified for the track. These mods are listed in my signature.

Last week I installed a 3 stage intake and AA stage 3 ECU tune. Tomorrow AA headers go in. The added power and torque changed the character of my car from Camry-like to what I think a BMW should do. It isn't neck-snapping fast, but there's a sense of urgency and pull that wasn't there before. Have a dyno appt. in a couple of weeks to capture numbers.

In an effort to capture data, I've been doing some max-launch 0 - 60 pulls. I don't really care about 0 - 60 times, rather I simply want some objective numbers to assess performance. Best time wa 6.1 sec. Most times are high 7s - mid 8s. The motor feels plenty strong, but the shifting mucks things up.

Now to the meat....

When launching the car, the transmission 'stutter shifts' between 2nd and 3rd in DS mode. The computer lets the motor run to 7k in 2nd then downshifts to 5k in 3rd. The motor spins up to 5.5 - 6k, then the trans drops again to 5k.

From searching, it seems there are three options:

- TCU adapter reset (car in accessory mode, throttle down for 30 sec, start car)
- TCU firmware flash (SIB 24 03 02)
- Trans fluid / filter flush and Mechatronics service

I tried to reset the adapter, with limited results. Is this the correct hierarchy of fixes? Do I need to a $400 TCU re-flash?

Anyone deal with this and have a fix?

Thanks.

[Cloud9blue]

Sounds like the clutch holding the planetary gears for 3rd gear is slipping. How many miles on the car, assuming you are still on stock transmission oil? It might not be a bad idea to switch out the oil and do a transmission reset.

[tetsuo111]

Originally Posted by Cloud9blue

Sounds like the clutch holding the planetary gears for 3rd gear is slipping. How many miles on the car, assuming you are still on stock transmission oil? It might not be a bad idea to switch out the oil and do a transmission reset.

Thanks Cloud9Blue. To be clear, mine is (sadly) AT, not MT. About 30k miles on the car, I bought it last Oct with 25k. I haven't changed the trans fluid, and would be surprised if the previous owner serviced the trans fluid, seeing as BMW recommends lifetime without flushing. I have done the transmission reset. This helps, but doesn't solve the problem.

I just spoke with a race-oriented shop about an unrelated issue, and mentioned this. He suggested checking the transfer case. Of course, this was an over the phone diagnosis, but it's some direction.

I think that I'll swing by the dealer today, and see what they have to offer.

[Cloud9blue]

Originally Posted by tetsuo111

Thanks Cloud9Blue. To be clear, mine is (sadly) AT, not MT. About 30k miles on the car, I bought it last Oct with 25k. I haven't changed the trans fluid, and would be surprised if the previous owner serviced the trans fluid, seeing as BMW recommends lifetime without flushing. I have done the transmission reset. This helps, but doesn't solve the problem.

I just spoke with a race-oriented shop about an unrelated issue, and mentioned this. He suggested checking the transfer case. Of course, this was an over the phone diagnosis, but it's some direction.

I think that I'll swing by the dealer today, and see what they have to offer.

Well, automatics uses various clutch packs inside the gearbox to lock the gear sets into whatever gear ratio it requires. I don't think transfer case would cause over-rev during gearshifts. If it is a CPO, just drop it off at the dealer then. But be sure to remove your ECU tune.