Cost of DCT Transmission Flush?

[aus]

Originally Posted by hugehead

and then do another change after a few miles to get the other half out

ps i was just quoting the info in the Bmw manual re DCT trasmission fliud change

If i had 40k miles on my M3 .....I also will be thinking of a transmission fliud change(but i've only 1180miles on mine at the mom and only do around 4k miles per year , so will not be changing in the near future lol )

That will get you to about 75% changed since you're only getting 50% of mixed oil out. This will get costly if you need to do 3 changes to get most of the oil out.

[swamp2]

Originally Posted by Radiation Joe

I just got one a couple of weeks ago. Mine may not be capable of cycling the pumps, however. Activations (cycling pumps) are part of the professional system. I just got the hobby version.

Hmmm, if the prof. system will really work for this I bet anything we could get a group buy together to get one and share it. Not a group buy per se but a shared buy. I know I would chip in for sure. It looks like if we get 7 or 8 folks we would be in for only $100 ea. Based on using the tool once every 2 years or so I be happy to chip in $100 and not have the tool in my possession.

[kenwelch]

Changing the fluid in a M-DCT is similar to automatic transmission fluid changes, you cannot get 100% of the fluid out. Fluid will remain in the hydraulic cooling plumbing, cooler, thermostat, oil-coolant heat exchanger, clutches, and Mechatronics module.

The pump that circulates the M-DCT fluid is driven by the transmission input shaft which turns only when the engine is running. The hydraulic pump is geared to the input shaft so the pump can only be operated by the running engine. There is no software control of the hydraulic pump. Software is used during the refill process to monitor the transmission fluid temperature for the achieving the correct level. Your scantool software needs to show transmission fluid temperature on the data list.

Some of the confusion might be that there is an “auxiliary coolant pump” located in the HVAC heater system. Cycling the “auxiliary coolant pump” will only move engine coolant through the heater core used for Heating Ventilation and Air Conditioning. The M-DCT hydraulic system uses an “oil-coolant heat exchanger”, that allows excess transmission fluid temperature to be passed to the engine coolant. The thermostat allows this to occur when the M-DCT fluid is above 95 degrees C. The auxiliary coolant pump is used when there is low coolant flow in the heater or when the M-DCT needs additional cooling.

Running the engine is the only way to move the M-DCT fluid in the cooler circuits
Shifting the transmission will allow the fluid to move in the clutches and Mechatronics module.

Multiple fluid changes would be the only way to change MOST of the M-DCT fluid.

Note: Typical automatic transmission flushing machines would not handle the higher hydraulic pressures used in the M-DCT.

[M3Bliss]

Originally Posted by kenwelch

Changing the fluid in a M-DCT is similar to automatic transmission fluid changes, you cannot get 100% of the fluid out. Fluid will remain in the hydraulic cooling plumbing, cooler, thermostat, oil-coolant heat exchanger, clutches, and Mechatronics module.

The pump that circulates the M-DCT fluid is driven by the transmission input shaft which turns only when the engine is running. The hydraulic pump is geared to the input shaft so the pump can only be operated by the running engine. There is no software control of the hydraulic pump. Software is used during the refill process to monitor the transmission fluid temperature for the achieving the correct level. Your scantool software needs to show transmission fluid temperature on the data list.

Some of the confusion might be that there is an “auxiliary coolant pump” located in the HVAC heater system. Cycling the “auxiliary coolant pump” will only move engine coolant through the heater core used for Heating Ventilation and Air Conditioning. The M-DCT hydraulic system uses an “oil-coolant heat exchanger”, that allows excess transmission fluid temperature to be passed to the engine coolant. The thermostat allows this to occur when the M-DCT fluid is above 95 degrees C. The auxiliary coolant pump is used when there is low coolant flow in the heater or when the M-DCT needs additional cooling.

Running the engine is the only way to move the M-DCT fluid in the cooler circuits
Shifting the transmission will allow the fluid to move in the clutches and Mechatronics module.

Multiple fluid changes would be the only way to change MOST of the M-DCT fluid.

Note: Typical automatic transmission flushing machines would not handle the higher hydraulic pressures used in the M-DCT.

Cool, nicely done. Great info.

[swamp2]

Originally Posted by kenwelch

Changing the fluid in a M-DCT is similar to automatic transmission fluid changes, you cannot get 100% of the fluid out. Fluid will remain in the hydraulic cooling plumbing, cooler, thermostat, oil-coolant heat exchanger, clutches, and Mechatronics module.

Hey Ken, thanks much. You need to post more often! Do you plan on changing your own fluid? Will you use the multiple change method to get most of the fluid out? Is there any other way to get more fluid out?

[kenwelch]

Originally Posted by swamp2

Do you plan on changing your own fluid? Will you use the multiple change method to get most of the fluid out? Is there any other way to get more fluid out?

As slow as my odometer moves it may be years for me to change the fluid. Looking at plumbing I don't think it would be simple to setup a flushing machine or find one that will handle the operating pressures.

I would likely use the multiple change method. Some members have driven their cars pretty hard at the track and they might need the fluid change.

Originally Posted by kenwelch

As slow as my odometer moves it may be years for me to change the fluid. Looking at plumbing I don't think it would be simple to setup a flushing machine or find one that will handle the operating pressures.

I would likely use the multiple change method. Some members have driven their cars pretty hard at the track and they might need the fluid change.

The heat exchanger, pipes, and even the transmission cooler doesn't hold more than a quart of fluid (approx around .5 quart).

Therefore, a drain and fill is more than sufficient. No need to do multiple drains and fills. Multiple drain and fills is required for an slush box is because of the torque converter. For example my 5HP19 ZF on my e46 holds about 2 quarts in the toque converter alone.

BTW...flushing the system is not hard. The hose fittings on the DCT is the same for any BMW power steering and automatic transmission. Just unlock them. The inner diameter of the pipes is ~.5-.6 inch so go and buy an .5 rubber hose.

flushing the DCT isn't no different than an automatic or power steering (high pressure)

[swamp2]

Originally Posted by ///Flash

The heat exchanger, pipes, and even the transmission cooler doesn't hold more than a quart of fluid (approx around .5 quart).

Therefore, a drain and fill is more than sufficient. No need to do multiple drains and fills. Multiple drain and fills is required for an slush box is because of the torque converter. For example my 5HP19 ZF on my e46 holds about 2 quarts in the toque converter alone.

The posts thus far indicate that about 50% of the total oil comes out during a drain, the rest remains in other parts of the system (lines, 2 exchangers, pumps, etc.). I can't verify this 50% number but to me that is far from a sufficient amount to get out during a fluid change. Would you do an engine oil change with 50% of the oil swaped for new?

Originally Posted by ///Flash

BTW...flushing the system is not hard. The hose fittings on the DCT is the same for any BMW power steering and automatic transmission. Just unlock them. The inner diameter of the pipes is ~.5-.6 inch so go and buy an .5 rubber hose.

flushing the DCT isn't no different than an automatic or power steering (high pressure)

Are you speaking from personal experience here, an educated guess or speculation? Which is it a flsh is not needed as you said above or it is as you discuss just after saying it isn't? Did you read the prior comments that you can not use typical automatic trans equipment to do this job? I'm sure a random rubber hose even of the correct OD with no fitting won't do the job... Similarly there are hoses and fittings all over this unit, you should specify exactly which hoses to disconnect and what to connect to for a proper flush.