So I am looking for a new truck. Problem is years ago I had a 4.0 in an Explorer that was mad! At 150K the timing chains had to be done and then at 160K the trans bit the dust...It was a money pit. I loved that thing however. In looking into a Ranger mid to late 2000's is their years to stay away from relating to engine and tranny problems?

 

The 4.0l SOHC engine had timing chain problems from 1997 to 2003, new design for tensioners solved the problems.
Although long timing chains can be issues in any engines, lol.
Rangers had 4.0l SOHC engines from 2001 to 2012

Automatics are a roll of the dice on used cars, simple as that
What kills all automatics is heat, so a vehicle with a 2nd trans cooler added would be a safer bet but still a roll of the dice.

The A4LD, 4R and 5R automatics didn't have any more issues than any other automatics, there were no "good or bad" years.

As said automatics are killed by heat, if a trans "feels" like it is slipping then it is, and that builds up heat inside, if you continue to drive it that way then trans will over heat and fail completely.
Slipping comes from lower pressure, slow or no Reverse is a sign of lower pressure.
Could be Valve Body gasket or solenoid is leaking a bit, not a hard fix.
But if left alone whole trans will get burned clutches and bands(brakes) because of low pressure, and full rebuild is required.


Manual transmissions are not the same gamble used, but they do need to have the clutch changed when it wears out so not without a down side