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Assuming your 2005 ExST is factory stock unmodifed & is 2WheelDrive (not 4WD)?
* Engine = V6~4.0L~SOHC
* Tranny = 5r55e.2WD, Compatible\Swappable with any 2001~2011 5r55e.2WD Tranny
* 4x4TransferCase = None
* 1997~2000 5r55e.2WD Transmissions are NOT Compatible\Swappable due to different Sensors+Case
* 1997~2011 5r55e.4WD Transmissions are NOT Compatible\Swappable due to different OutputHousing
5r55e Transmissions use MerconV ATF; capacity is 12~13qts.
Recommend every 6mths, suctioning ~1qt from TrannyDipTube & replacing with fresh MerconV.
Recommend every 33kMiles, a PanDrop & ATF+Filter Change & BandAdjust & new PanGasket;
this will change out about half of the ATF or 6~7qts.
Recommend every 100kMiles, new SolenoidPack & ServoORings & ServoGasket for the ValveBody.
5r55e.2WD Transmissions were stock fitted with Shallow2WD versions of the Pan & Filter;
recommend swapping these out to the Deeper4WD Pan+Filter, during the next 33kMile service.
Around 2002~2003 the 5r55e ValveBody was improved with a BondedGasket & other components.
If unserviced, 5r55e Transmissions are notorious for slipping & failing to engage Reverse\Drive.
Recommend a 2ndParallel or larger TransCooler, in the front grill, especially if you tow.
Hope this helps.