[BillyG]

Some time ago my 2007 e90 328xi developed an oil leak on the driver side of the engine. About 2 months ago it was traced to a broken aluminum bolt between the cylinder head and the block. I did the repairs myself, removing the intake manifold, and now the leak is gone. However, shortly afterwards I noticed that the automatic transmission does not shift to the 6th gear, even though all other gears seem to shift smoothly and correctly. On acceleration, it shifts up to the 5th gear at ~55 mph and stays there, no matter how fast I go (I tried going really fast), resulting in reduced highway gas mileage and high rpms (2700 instead of 2100 at 78 mph). The car also makes humming/buzzing noises at the speeds above 40 mph that normally occurred only when driving on some uneven highway pavements, except that now this happens on city streets that I’ve driven for years without such noise. I can't tell whether the noise comes from the new tires (see below) or the engine bay, but I thought I'd mention it anyway.
For the life of me I can’t remember whether the gear shifting problem began before or after the repairs. My wife, who does most of the driving, thinks it started before, because she remembers reduced gas mileage on highway since before the repairs, but she never paid attention to the tachometer.
Does anyone have any idea what can be wrong with my car? I didn’t do anything to the transmission besides cleaning its underbelly with an engine bay cleaner and a shop towel, so my first guess is that some sensing mechanism no longer works correctly.
I am also concerned with whether there could be any leftover problems after the external leak was stopped. It actually developed about a year ago, but it was minor, and I was too busy to fix it, so we drove the car as-is for almost a year. In all of this time, the total oil loss was only 1-2 quarts. Yet, most of the engine and the underbody splash guards ended up being smothered with oil. This makes me wonder whether the oil could have seeped into and filled other engine compartments it wasn’t supposed to (e.g. crankcase breather around cylinder bores), or if it could have cross-contaminated with another fluid, such as coolant. I did find 1-2 oz of engine oil in the intake manifold body after removing it. I know little about the engine internals, so any insight is welcome.
Some miscellaneous details. The broken bolt was on the front side of the engine exterior, near the timing chain and right under the frontmost finger of the intake manifold, so the manifold had to be removed. I replaced a broken bolt with an OEM part and torqued it to spec from Bentley. All other parts were reused. I inspected and cleaned the intake manifold gaskets, but they were in a surprisingly excellent condition (no cracks, good elasticity, no excessive compressional deformation), so I didn’t change them. The car has 98K miles on it, brand new all-season tires installed in early summer. I use only 93 octane gas. The car is driven mostly on highway in winters and in town in summers with a fairly moderate driving style. For the sake of completeness, I’ll mention that I also drained the power steering fluid through a banjo bolt while the car was apart, although I’ve done this before, and I don’t see how this could be relevant to my symptoms.

[BashShah]

Seem like you know your car.
But how many k.

If over 80k, have considered changing tranny oil.
Inspect and maybe change Machatronic Sleeve.
Most common area for leaks.

Also, will look up another thread that I read that might give you a starting point.

But I don't think it's your engine.
Sound like a solenoid for the 5th and 6th gear in the tranny.

DN

[BillyG]

The car's got 98K miles on it, so I will read up on changing transmission oil and the sleeve. Thank you for all your suggestions! I will look into them, hopefully, next weekend. Any suggestions on how to test those solenoids? Also, please post the link you had in mind, if you find it.

[BashShah]

Fu!k took me 2 hours on my iPhone to find this link.

http://www.e90post.com/forums/showthread.php?t=479837

I am not 100% sure this is your problem, but you problem can be 1 of 3 things.

1. Mechatronic Sleeve leak... Doubt it.
2. Transmission Solenoids....The above link....possibly.
3. Torque Converter..... But this is time consuming, and it would be affecting 1-4 shifting more than 5-6.

I was also figuring that since you are due for a tranny oil change so this would be the time to change out all the Solenoids.... Just to be sure.

If you google and eBay enough, I am sure you will find cheaper.

http://www.thectsc.com/index.php?p=p...d=36&parent=52

DN