420k and counting on my early 99, 6-speed manual. I spent the dough last summer to rebuild the turbo with a bigger turbine wheel and billet compressor wheel, and a programmer. Towed the 12k boat+trailer twice to the top of Vancouver island, first stock, second with the programmer set to 20hp tow setting, and modified turbo. Night and day difference; no downshifting on the lower island's rolling hills, and big power pulling the hills on the upper island. Stock I was in between direct and overdrive all the time on those mild rolling hills.
Stock it had less poop than a 7.3IDI with aftermarket turbo. That's not much poop.
It is a mix of lots of complicated parts, but generally they're reliable and easily diagnosed. Every 7.3 owner has a cam sensor and 10mm wrench in their glovebox, and every 7.3 at some point needs new glowplugs and injectors, and some top end oil sealing and fuel bowl rebuild work, none of which is difficult. My injectors are stock at 420K...I'm entertaining a swap but will see how this tow season unfolds. Will probably do some compression/leakdown checks before swapping injectors. I bought the truck cheap, have put in some money/effort on springs/shocks/brakes, engine top work (fuel bowl and high pressure oil), and some comfort items (soundproofing and better seats) and now it works great and doesn't owe me much.
It doesn't take much work or modification to harness the big 7.3L displacement and blow the pants off of any non-variable-vane single-turbo 5.9 cummins, of any configuration. Big 5.9 power with a single turbo is certainly available, but you can't have that cake and eat it too: low rpm power is replaced by clouds of smoke. Different story with the variable vane turbo on the 6.7 cummins; that one is a monster.
It's kind of a shame that gas engines have gone from late 70s 7.5:1 low-compression hot constipated big blocks (454 and 460, carbed and fuel injected) to high-strung fuel suckers, with zero reprieve. GM's 8.1L was getting close to sanity, but it too was constipated by poor head port design and engine air/fuel programming. Ford's new 7.3 gas should be a welcome change back to real big block gas power.
Diesels with EGR, SCR, Exhaust Filtration and such are non-starters for me. Way too much drama. Next truck will be big block gas, old or new. If old, the engine will be modified to address poor compression and quench and increase airflow. A 454 or 460 making legit 400hp at 4500-5000 rpm should be a monster.
