My girlfriends 07 acura mdx had to have the transmission replaced. Now the mechanic calls and says something about milkshakes and the radiator needs to be replaced. He's talking like I'm supposed to know wtf a radiator milkshake is. Can anyone give some guidance and explain how this issue would come up while changing a tranny out?

 

Here's a thread from the Ridgeline forum that illustrates the infamous 'strawberry milkshake of death' and why it occurs. This issue plagues the Pilot, Ridgeline, MDX, and other makes and models too... not just Honda. It's my understanding the new Denso radiators have corrected this issue, but there are many older vehicles out there from Honda, Nissan, and others who share this common design. Note there are only 1/8 of threads that hold the heat exchanger (at the bottom of the radiator) in place. When this connection fails, coolant can enter the transmission and if not stopped immediately, fatal transmission damage can occur. The tell-tale sign is when the coolant looks like strawberry milkshake.

To be proactive about this, many owners are replacing the radiator at the time of the timing belt/water pump service.

Pictures of corroded/rusted radiator fittings - Honda Ridgeline Owners Club Forums