My automatic transmission was over a quart low on fluid but there are no leaks. Where else could the fluid go?
First check the radiator to see if the coolant is oily. A leaking transmission cooler can allow leakage into the radiator. Also if the radiator has been replaced, transmission fluid is often loss. If the shop did not check the transmission, it may have not been refilled. Lastly, if a transmission service has been performed, the proper amount of fluid might not have been replaced. For much more on proper transmission service, see our article Transmissions and proper service.