Here is the full list of all 48 DiRT 4 achievements worth 1,000 gamerscore. It takes around 60-80 hours to unlock all of the achievements on Xbox One.
Won the Triple Crown
Achieved 10 Gold medals in Joyride
Set a Gold medal time in a Time Attack challenge without hitting a penalty marker
Won the Historic Legends Series
Earned the International Rally H-A licence
Destroyed 100 blocks in 60 seconds in Joyride
Completed 25 Events in Pro Tour
Got promoted to a new Tier in Pro Tour
Completed all 12 Stages of a Monthly Event in Community Events
Completed back to back Weekly Community Events
Won the Landrush World Series
Won the Global Rally Series
Repaired your car on Stage and won the Stage
Earned the National Stadium Pro-1 licence
Completed a Stage or race with the Fearless Preset active
Owned a vehicle equipped with all Grade A parts
Bought a vehicle from the Classifieds
...it's gonna be a long week
Upgraded three Facilities to Grade A quality
Won the FIA World Rallycross Championship
Finished in the Top Tier of a Delta Daily in Community Events
Finished in the Second Tier or higher of a Daily in Community Events
Hired a fourth Engineer onto your Team
Completed all of the Advanced Driving Techniques at the DiRT Academy
Qualified in the top spot of a Rallycross Event in Career
Set a time in every challenge in a single Joyride Chapter
Earned the International Off-Road C-1 licence
Qualified for an A-Final in a Landrush Event in Career
Earned the International Off-Road C-3 licence
Earned the International Rally R-1 licence
Earned the International Rally H-C licence
Took two Joker Laps and won a Rallycross race
Finished a Stage in sunny conditions in Community Events
Finished three sectors of a Stage with a flat tyre
Earned the International Rally R-3 licence
Won a Stage at night
Earned the National Stadium Pro-3 licence
Cleanly landed a jump longer than 65m
Won a Stage in Headcam
Got an overall win in the lowest eligible Vehicle Class in a Rally Event in Career
Won your class in a multi-class Event in Career
Triumphed in the face of adversity
Earned the Fearless Bonus in a Stage or race
Called in the Chief Engineer's recommendations during a Service Interval
Finished in first place in a Career Event
Completed a clean Stage or race
Completed an Event in Jam Session
Completed the Welcome Event