Here is the full list of all 48 DiRT 4 achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
Complete 25 Events in Pro Tour
Destroy 100 blocks in 60 seconds in Joyride
Complete all of the Advanced Driving Techniques at the DiRT Academy
Complete all 12 Stages of a Monthly Event in Community Events
Win the Landrush World Series
Earn the National Stadium Pro-1 licence
Win the Global Rally Series
Complete a Stage or race with the Fearless Preset active
Get promoted to a new Tier in Pro Tour
Achieve 10 Gold medals in Joyride
Complete back to back Weekly Community Events
Complete an Event in Jam Session
Finish in the Top Tier of a Delta Daily in Community Events
Get a bad case of the Mondays
Take two Joker Laps and win a Rallycross race
Triumph in the face of adversity
Win the FIA World Rallycross Championship
Own a vehicle equipped with all Grade A parts
Qualify in the top spot in a Rallycross Event in Career
Hire a fourth Engineer onto your Team
Upgrade three Facilities to Grade A quality
Earn the International Rally R-1 licence
Win a Stage in Headcam
Earn the International Off-Road C-1 licence
Win a Stage at night
Finish in the Second Tier or higher in a Daily in Community Events
Set a time in every challenge in a single Joyride Chapter
Finish a Stage in sunny conditions in Community Events
Finish three sectors of a Stage with a flat tyre
Buy a vehicle from the Classifieds
Earn the International Rally H-C licence
Earn the International Off-Road C-3 licence
Set a Gold medal time in a Time Attack challenge without hitting a penalty marker
Qualify for an A-Final in a Landrush Event in Career
Earn the International Rally R-3 licence
Earn the National Stadium Pro-3 licence
Get an overall win in the lowest eligible Vehicle Class in a Rally Event in Career
Win your class in a multi-class Event in Career
Call in the Chief Engineer's recommendations during a Service Interval
Earn the Fearless Bonus in a Stage or race
Finish in first place in a Career Event
Complete the Welcome Event
Complete a clean Stage or race
Cleanly land a jump longer than 65m
Earn the International Rally H-A licence
Win the Historic Legends Series
Win the Triple Crown
Repair your car on Stage and win the Stage