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7 Series - E38 (1995 - 2001)

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  #1  
Old 08-20-2010, 01:28 AM
HLB HLB is offline
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Location: Australia
 
Join Date: Feb 2010
Posts: 74
Mein Auto: 1997 740il
97 740iL - Transmission

Hi there,

I have noticed when I first use my car after it has been standing, for example while I am at work, my car takes a while to change gears.

So when I take off, I can be travelling along and it takes quite a few revs (2,800) to change gears. After one or two gear changes, the transmission acts normally and gear changes as are hardly noticeable.

Generally I like to change gears manually because I don't like to stress a cold engine, as I need to get the revs up for it to change.

Is this something to do with cold trans fluid?

No lights on dash or anything.

At operating tem, it is perfect.

Is this normal?

Any ideas?
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  #2  
Old 08-20-2010, 06:50 AM
balance balance is offline
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Location: NC
 
Join Date: Feb 2009
Posts: 758
Mein Auto: 97 740iL
Completely normal. My 740 does the same thing. The ECU controls the shift points and makes the transmission shift at a higher RPM to make the motor heat up faster until it reaches 65 celcius on the unlocked information display. I have heard that shifting manually is not a good idea, as the transmission was not designed for this.
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  #3  
Old 08-20-2010, 03:19 PM
HLB HLB is offline
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Location: Australia
 
Join Date: Feb 2010
Posts: 74
Mein Auto: 1997 740il
That's great. Thanks for the reply. That makes sense, it doesn't take much distance distance/many initial automatic changes at all so I'll let the computer do its thing. Computer knows best.
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  #4  
Old 08-22-2010, 01:42 AM
HLB HLB is offline
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Location: Australia
 
Join Date: Feb 2010
Posts: 74
Mein Auto: 1997 740il
I have since come across an interesting paper on our transmissions.

This all makes perfect sense...

Engine Warm Up Cycle
The transmission shift points are modified after cold start to raise engine RPM during shifting.
This allows for a faster engine warm up and reduction of catalyst warm up time. The
TCM uses the transmission oil temperature information to determine the implementation of
this function.
The warm up phase program will be terminated if any of the following conditions exist:
The vehicle exceeds 25 MPH or
Transmission oil temperature exceeds 60 Degrees Celsius or
A Maximum of three minutes is exceeded.

Found in: http://e38.org/electran1.pdf
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