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9 Posts

Posted - 10/28/2012 :  09:39:21 AM  Show Profile  Visit barser's Homepage  Reply with Quote
04 Frtl with Mercedes MBE900 and Allison 2000. After replacing headgasket in the engine the trans don't seem to shift properly. No codes in engine, ABS or trans. The engine RPM will fluctuate 300 to 400 RPM. Its not noticeable in 1st but does this in 2, 3, 4 & 5. It does it with moderate or full throttle. The current gear on the data does not change when the RPM changes. The engine seems to run normal and has good power. We are many miles away from a dealer so any help will be appreciated

Advanced Member

United States
490 Posts

Posted - 10/28/2012 :  2:14:32 PM  Show Profile  Reply with Quote
First douple chack all connectors tomake sure that allis will and that you have no bent pins from reassembly from the repair.

The transmission could have picked up some bad habits when it went into quick-learn mode afrter the repair.
Once "fast learn" mode is initiated:
- drive the bus at 1/4 to 1/2 throttle
- accelerate to 2000 rpm and lift the throttle to intiate upshifts
- on hills, feather back the throttle until 1300-1400 rpm befor pushing down enough to initiate a single gear downshift.

I seem to have lost the order for the selector dance needed to trigger a Fast Learn mode. Any body have it? I seem to remember something about simultaneously clicking my heels together, patting my head and rubbing my belly.....

I may not know the answer but I can usually find who does.
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Kid Grimy
Active Member

12 Posts

Posted - 10/30/2012 :  09:42:59 AM  Show Profile  Reply with Quote
On an Allison 2000 adaptive shifting is learned by driving the bus. The shift pattern is learned by the transmission control module (TCM) after receving information from the throttle position sensor (TPS) and the netural start backup (NSBU) or internal mode switch (IMS). Like JustinB said, drive the bus in different modes (we just drive them normal for awhile) and it should get rid of its old shifting habits.

Kid Grimy
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