...just bought a 2001 Ranger Extra Cab 4.0 V6 4x4 with 144k miles
...odometer wasn't working when i bought it so no telling how many actual miles
...list of things that I've found that were either broken or missing
Welcome to the Herd; lots of friendly knowledgable folk in these forums!
Retired engineer myself; have here a 2001 SportTrac, close sibling to 2001 Ranger ExtraCab V6 4WD;
same Frame, WheelBase, Engin, Trans, TransferCase,... but with full backseat & ultrashort bed.
Notes on a few of the NotoriousFailureItems\NFIs:
* OilPressurized TimingTensioners, renew every 100kMiles\12yrs
* JunkPlastic ThermoStatHousing, swap to an Aluminum version
* JunkPlastic HeaterControlValve, swap to an Aluminum version
* JunkPlasticTanked 2Core Radiator, swap to a 3or4Core AllAluminum version
* PCVValve Coolant Loop, delete 5/16" Tees+Hoses+OxbowCollar+MiniExchanger, useless source of leaks
* 5r55e Trans, every 33kMiles\4Yrs: drop Pan, new VB BondedGasket, retorq VB Bolts, new Filter, new PanGasket, new 5~7qts MerconV, adjust Bands
* InstrumentCluster+DashCenterPanel Bulbs, renew every 100kMiles\12yrs
* 1354 TCase, every 33kMiles\4yrs: MerconLV Drain+Refill,
TestDrive 2WHi~4WHi~4WLo once a month, replace 4x4ShiftMotor\ConModul as needed
* RearDiff, every 33kMiles\4yrs, 75w140+SlipAdditive Drain+Refill
* FrontDiff, every 33kMiles\4yrs, 75w90 Drain+Refill
* FrontWheelHubs, check slop every 33kMiles\4Yrs, replace as needed
* ...
Click signature below for more info.
Hope this helps.