I’ve had a lot of discussions here lately about which diesel engines are the best and worst. Is the 6.0 as bad as people say? Is the 7.3 the best ever? Let’s settle it here.
Wow, this thread really blew up! Thanks to everyone for sharing your thoughts and info! Also, I’ve started a new forum called Mechanical Helpers, come check it out.
Here’s my ranking for Ford, best to worst: 6.7, 7.3, 7.3/6.9 IDI, 6.0, 6.4. You could argue 7.3 over 6.7 or 6.0 higher, but everyone agrees 6.4 is last.
Reilly said:
Here’s my ranking for Ford, best to worst: 6.7, 7.3, 7.3/6.9 IDI, 6.0, 6.4. You could argue 7.3 over 6.7 or 6.0 higher, but everyone agrees 6.4 is last.
Agreed. Ford really nailed it with the new Power Strokes.
Reilly said:
Here’s my ranking for Ford, best to worst: 6.7, 7.3, 7.3/6.9 IDI, 6.0, 6.4. You could argue 7.3 over 6.7 or 6.0 higher, but everyone agrees 6.4 is last.
I’d rank the 6.0 above the 6.9/7.3 IDI because of power. I have a 6.0, and once it’s bulletproofed, it’s solid. My 7.3’s 4R100 transmission has been rebuilt twice already. It’s not great.
@Sky
How do I know if my 4R100 has a PTO? Did they ask you about it when you rebuilt yours?
Vernon said:
@Sky
How do I know if my 4R100 has a PTO? Did they ask you about it when you rebuilt yours?
If you have a PTO unit, there’s an 8"x6" cover on the side of the transmission. Take it off, and you’ll see the gear unit.
Reilly said:
Here’s my ranking for Ford, best to worst: 6.7, 7.3, 7.3/6.9 IDI, 6.0, 6.4. You could argue 7.3 over 6.7 or 6.0 higher, but everyone agrees 6.4 is last.
Before the 6.4 inevitably melts a piston, those compound turbos are a lot of fun!
Reilly said:
Here’s my ranking for Ford, best to worst: 6.7, 7.3, 7.3/6.9 IDI, 6.0, 6.4. You could argue 7.3 over 6.7 or 6.0 higher, but everyone agrees 6.4 is last.
Why do people say the 6.4 is so bad? I’ve argued with folks who say the 6.0 is the best, and I just don’t get it.
@Reign
The 6.4 is awesome for about 100,000 miles, then it’s toast, and you’re out $10K for a new engine. For a diesel, that’s awful.
Indigo said:
@Reign
The 6.4 is awesome for about 100,000 miles, then it’s toast, and you’re out $10K for a new engine. For a diesel, that’s awful.
With how expensive new trucks are, I’d gladly pay $10K for a new motor every 100K miles and still come out ahead financially. Half a million miles for way less than a new 6.7? Yes, please.
@Kim
I’ve always wanted to buy a blown 6.4 and do a Cummins swap. Just don’t have the time!
Indigo said:
@Kim
I’ve always wanted to buy a blown 6.4 and do a Cummins swap. Just don’t have the time!
Fummins swaps are cool but often turn into electrical nightmares. Still, the idea is tempting.
@Kim
Taylor Ray did one about a year ago, and it’s still holding up well.
Emory said:
@Kim
Taylor Ray did one about a year ago, and it’s still holding up well.
Not saying it can’t be done well—someone below mentioned their swap is great.
@Kim
But 6.7s are more reliable and not much more expensive anymore. The downtime and repairs with the 6.4 wouldn’t make up the difference.
Reilly said:
@Kim
But 6.7s are more reliable and not much more expensive anymore. The downtime and repairs with the 6.4 wouldn’t make up the difference.
I paid $42K for my 2009 F-350 new. A 2015 F-250 with 105K miles costs almost the same now. My 6.4 has been rock solid—no major issues. I just don’t see a new truck as a better value.
@Kim
A good 6.4 build that lasts will cost you $20K–$25K.
Perry said:
@Kim
A good 6.4 build that lasts will cost you $20K–$25K.
LOL, ‘quality’ 6.4, good one! 
Perry said:
@Kim
A good 6.4 build that lasts will cost you $20K–$25K.
I’m at 102K miles with no problems yet. When I priced a rebuild, it was around $18K including labor. Still cheaper than a new truck.
@Reign
The 6.4 is flawed by design, and no amount of upgrades will fix it. The 6.0, once upgraded, becomes a decent motor. The 6.4? It’ll always fail.