1stDeuce
Explorer
117k? "High mileage"?? I consider high mileage something over 200k. Like 300k. That would be high mileage for me. 
And Cole is pretty much right. I was in the TJ vehicle develpment group at DCX from '99-2003. Emissions were getting tough on the 4.0L, but it still hadn't gone to EGR, and wile "intrusion" was a concern on platforms with a short nose, it wasn't really on TJ.
The real reason the 4.0L went away was because DCX had too many "six cylinder" engines at the time, and the big guys in the corporate "powertrain" group wanted to kill it off and replace it with a more common engine. The 3.8L that the JK got wasn't spectacularly "high tech", it was just already in production. In a sad bit of irony, the 4.0L had the lowest warranty cost of any engine in the company when the decision was made to retire it. As many '2003+ TJ owners can tell you, a problem with cam sensor fit drove warranty up shortly after that decision was made.
We thought it made more sense to modernize the 4.0 a bit and put it in the Dakota platform, but they cited the antiquated design... All while GM got all sorts of awards for the inline 5's and 6's they developed around the same time. And so JK got the minivan 3.8. The same drive for reduced engine count pushed the 2.4L into the TJ earlier, in 2003. The 2.5L was a far superior "jeep" engine, but TJ was the last platform using it.
On the plus side, with Chrysler selling as many JK's as they can build, they likely get a little more attention from the powertrain group these days...
Chris
And Cole is pretty much right. I was in the TJ vehicle develpment group at DCX from '99-2003. Emissions were getting tough on the 4.0L, but it still hadn't gone to EGR, and wile "intrusion" was a concern on platforms with a short nose, it wasn't really on TJ.
The real reason the 4.0L went away was because DCX had too many "six cylinder" engines at the time, and the big guys in the corporate "powertrain" group wanted to kill it off and replace it with a more common engine. The 3.8L that the JK got wasn't spectacularly "high tech", it was just already in production.
In a sad bit of irony, the 4.0L had the lowest warranty cost of any engine in the company when the decision was made to retire it. As many '2003+ TJ owners can tell you, a problem with cam sensor fit drove warranty up shortly after that decision was made. We thought it made more sense to modernize the 4.0 a bit and put it in the Dakota platform, but they cited the antiquated design... All while GM got all sorts of awards for the inline 5's and 6's they developed around the same time. And so JK got the minivan 3.8. The same drive for reduced engine count pushed the 2.4L into the TJ earlier, in 2003. The 2.5L was a far superior "jeep" engine, but TJ was the last platform using it.
On the plus side, with Chrysler selling as many JK's as they can build, they likely get a little more attention from the powertrain group these days...
Chris
Last edited: