+1 ^^^
4.0l SOHC was a good reliable engine, used from 1997 to 2011/2 in these Ford models
1997–2010 Ford Explorer/Mercury Mountaineer
2001–2012 Ford Ranger
2001–2010 Mazda B4000
2005–2010 Ford Mustang
When it was first used in Explorers in 1997 as an option/upgrade from the 4.0l OHV it was fine
Then a few years later they started to get "the rattle", Ford chocked it up to lack of service(no oil changes) by owners........
But soon Ford Dealers were complaining that some of their customer's 4.0l SOHC engines, which had PERFECT service records, where also getting "the rattle"
So Ford had a look
Seems that the 2 long chain tensioners on this engine were failing to hold the chains tight on startup before oil pressure took over
So on each startup the chains would BANG on the guides, over time a guide would break, and you get "the rattle"
So "the rattle" means Damage Done, have to change broken guide, there is no "warning signs"
Usually it was the rear guide so engine has to be pulled out to replace it
The chains and guides were fine it was THE TENSIONERS that were the issue
So back to the drawing board to redesign the spring loading needed to hold the chains tight on startup
New design tensioners were put into production and were used at engine assembly plants in 2002/3, and then these engines went into 2003/4 Model Year Vehicles
So if you have a pre-2005 Ranger with 4.0l SOHC it wouldn't be a bad idea to get 2 new Motorcraft tensioners and install them, they are not hard to get at and install
And I would change them every 100k miles just as general service on any year 4.0l SOHC
This was NOT a 100% failure rate, it seems there were just "some" tensioners with the old design that failed, I don't think there are any percentages for a failure rate, but a guess might be 10%
You have a 5R55E automatic, used from 1985/6 to 2011/2 in Rangers and other Ford models
So 26 years, no car maker keeps a "bad" engine or transmission around for 26 YEARS, lol
It is an automatic................................so when there is a problem its a "boat", bust out another thousand
Service it and don't overheat it and it will last
You want a manual transmission if you want longevity