Well, I've got one of the "hotter" 6.5's around. It will tow my 8500lb, 34 foot travel trailer anywhere. When I say everywhere, I mean
everywhere.
Prairies, Appalachians, all over the Rockies. Vantage highway, Butte, 4th of July, grapevine, all of it. Here's our last long pull:
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Unloaded it can get around 18 mpg combined. That's a K2500 ECLB with 4:10 finals. When mine was a stocker, you could count on around 13-14 mpg. Coincidentally, mine gets around 13-14 mpg hauling our monster trailer after the "upgrades" were done.
Now, after such a positive sounding start and from a guy who some might think would be the biggest supporter of 6.5's, here's the shocker:
I do not recommend you buy a 6.5 TD.
Not unless you're willing to sink stupid amounts of cash into it and get mediocre results for your efforts. Mediocre towing performance. Mediocre MPG performance. Mediocre reliability. Acceptable daily driving but unacceptable NVH performance.
In stock form, they are crap. They lack power. They overheat. They fracture main webs. They break cranks. They have pull-your-hair-out-and-shoot-yourself-in-the-face electrical problems. Injection pumps are suspect unless you have the newest update with ceramic components. and on, and on and on.....
The reason mine is reliable and powerful can be boiled down to one number: $20,000+
That's the purchase price of the truck and fixing all that is wrong with them.
Here's a brief list:
Purchase price 1998 K2500 ECLB - $5,000
OEM Engine (the second one by the way) cracked the main webs and cracked a piston crown - replaced with a new optimizer for $10,000 (includes labor since we were on a trip)
Injectors (done twice) - $800
Harmonic balancer (fluidampr, OEM's are pointless) - $500
Computer recalibration (stock calibration is crap and the biggest problem with power) - $600
PMD relocation kit and new PMD (absolutely essential for every electronic 6.5) - $500
Water meth injection (needed if you don't want to overheat pulling long hills) - $500
New Standyne updated pump for ULSD - $1500
3"/4" Turbo back exhaust - $400
Bigger oil cooler and SS lines - $400
HO water pump - $150
Right there I'm over 20,000 and I could go on with lots of maintenance items I had to do. But that list about what is essentially
JUST the engine. I'm probably closer to 23-25,000 into the truck by now but it makes me sick to think about it. Had I not been so "pig headed" about getting a GMT 400 (and wanting to "cheap out" on the purchase at first), I could have had a nice LB7 Duramax that would be around 4-500 rwhp and would tow more than I could ever want. With more potential should I ever want to tap it.
You can cheap that list out some, but you're sacrificing something somewhere. For example: you can buy a military take out 6.2 for around 2 grand vice the 7 it will cost for a new GEP engine. That will save you 5 grand. But: they are NA engines. No piston oil cooling jets, smaller precombustion chambers instead of the larger turbo chambers and among other things - you're taking your chances on whether or not you will have to rebuild it when you get it. There goes most of your 5 grand.
If you get an older 6.5, you can start adding things like replacement turbo, later style cooling upgrade parts (mid 97 is when it started), etc, etc...
The biggest problem is that GM cast engine. It's crap and needs to be replaced with a GEP/Navistar redesigned casting. There is only two types of OEM blocks: those that have failed or those that are going to fail. A running OEM block is a ticking time bomb. I have yet to pull one apart (running or not) that isn't cracked in the main webs. Even the supposedly "best" 599 casting (that was the last one I blew up by the way). The crack main webs, nodular iron cranks break, they crack cylinder, the heads crack in the water jackets between valves, the starter pad mounts break off, and on, and on....
And the 6.5 is anything but refined. It's loud. I mean my wife hates it loud. Believe me, I know how to tune a 6.5 and it's not getting any quieter than it is now.
Even with all this money I'm still only pulling 250 RWP and around 470 lb/ft. That's only stock LB7 territory.
Really, unless you plan to drive it till it drops or have very deep pockets, avoid the 6.5 trucks.
There's a reason why they a cheap to buy in.
It's not a good design for a truck that pulls any kind of weight or (at the age they're at now) needs to be reliable. Power is not very good at all, not much better than a stock 350 in the same chassis. 454 is a better tow pig in stock form, but you pay for that in MPG. A used LB7 truck would make a good puller and return good mileage. They are also getting relatively affordable. The problem with LB7 trucks are the injectors. They are prone to leaks and failure and are hellacious expensive. As in thousands to replace expensive.
Again, I really advise against buying a 6.5. Especially if you are "cash strapped".
Towing heavy and affordable are not really words that go together.
