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Join Date: Oct 2001
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I've been through this and researched all the options and here is my analysis:
The SMG hydraulic unit costs about $3500.
It consists of 3 main groups:
The pressure system (pump/accumulator), the slave cylinder, the solenoid assembly.
The pressure system parts as well as the slave can be purchased separately.
If the system leaks, it's almost always the slave.
A leaky system will always generate pressure errors as will pump issues and solenoid issues.
So it is VIRTUALLY impossible to tell if if you have more than one issue that is affecting the unit.
The codes are normally: pump on time excessive and pressure undershoot issues.
BMW generally recommends replacing the entire SMG Hydraulic Unit if you have pressure issues or any leaks.
This is very good advice because:
a) You will end up dropping the transmission multiple times if you don't solve the problem with the first replacement
b) You may end up not being able to solve the problem with incremental replacement and end up having to replace the hydraulic unit and paying much more because the invididual parts are not cheap or returnable
The most cost effective solution in the face of leaks/pressure issues is to replace the hydraulic unit.
There is IMHO no other sensible way forward.
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Last edited by sikand; 30th September 2011 at 11:05 PM.