Ok so I accidentally put transmission fluid in the def tank on a f-550 dump truck at work today. I only put 2 quarts in though. What's going to happen?

 

No ones knows what will happen ?

 

Oil and water based Urea are not going to mix in an intended and fairly sterile system. Oil into the system is never good for DEF/SCR Catalyst systems even in trace amounts. Putting DEF into the fuel would have been very expensive, but the trans fluid,, the tank should be cleaned, and all of the contamination removed. Running the truck with the contamination can/would possibly damage an expensive system. Even a system run with only water added to the DEF will result in running issues.