Cadillac 2011 STS Owner's Manual page 373

It is not necessary to check the transmission fluid level.
A transmission fluid leak is the only reason for fluid
loss. If a leak occurs, take the vehicle to the dealer
service department and have it repaired as soon as
possible.
The vehicle is not equipped with a transmission fluid
level dipstick. There is a special procedure for checking
and changing the transmission fluid. Because this
procedure is difficult, it should be done at the dealer
service department. Contact the dealer for additional
information or the procedure can be found in the service
manual. To purchase a service manual, see
Change the fluid and filter at the intervals listed in
to use the fluid listed in
.
.
, and be sure
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