This thread could go on FOREVER with different members saying " I have a ______ Explorer _ _ _, with a ________ engine, and I have x..,000 Miles, and never had a problem...."
But the truth of the matter is this:
The 4.0L OHV is a good engine, but it had Headgasket issues, which caused overheating and that led to cracked head issues....
The 4.0L SOHC has timing chain reliability issues.....if they could perfect THAT problem, there wasn't anything else wrong with that motor....
And behind BOTH those motors were some variant of the A4LD/4R/5R in auto form, or a M5OD-R1 or the HD version....and we ALL know how well those hold up.....
OR you could have the 5.0L V8 engine, with the 4R70W transmission.
Given the progression of the 5.0L, and the Explorers recieved the VERY LAST ONES, says it was as far advanced as Ford could have taken it, in OEM form....and the 4R70W is a VERY proven platform. In fact, Ford only upgraded a couple parts on the 4R70W since the last Explorer rolled off the assembly line almost 10 years ago!
The 2WD version of the 5.0L/4R70W is HANDS DOWN the most reliable drivetrain option for any Explorer from 1991-2010.
The 2nd most reliable is the AWD version of the same vehicle....Only because the BW4404 transfercase will never be as reliable as not having one in the first place....
Ryan