How many miles do they run at this gross for at a go?
they are strain testing gearboxes and diffs.

I'll be Honest, Australia is utilised as the worlds proving ground for heavy equipment, due to the fact our conditions, Road ambient and ETC, are widley recognised as the harshest in the world.

can you imagine hauling that 286K lbs load at 55 mph for 12 hours with nearly no rest?

Honestly, our gear works hard, and if there is even a small flaw, it rears its head.

__________________
Life is like a ride on the Freeway, Dodging bullets while your trying to find your way.

Theres more to life than only surviving.

Not to mention you guys are upside down. Lubrication is probably an issue when your truck is always driving on the bottom of the planet.

I believe that I do know how hard it is on an engine to run like that. I have taken part in some torture tests on engines that would make you cringe. The problem is the small flaw. As long as an item is made by human hand with human engineering stuff is going to break. It is just a matter of what goes first and when. I have only had the experience of being on a wrecker once. Wheel bearing on a new truck went out with 65 miles on it. How's that for luck. The first cato failure that I saw was out of a tri axle wrecker. Grenaded number 4 cylinder. Nice pretty yellow peterbilt was then black with oil. Nobody wants it to happen to them, except mabey me. I really do not care what happens to the engine, it all pays the same. I guess that we can both agree that I a little skeptic, but it is my nature sorry.

I would imagine an engine is working at max from 0 to top speed is the same reguardless of load,,, you hit max, its max, now for sustained speed im sure your working harder than my 129,000 but we race there and race back granted empty ,,, to load again and again for ten hrs straight most of the time.off road dust in nevada along with nevada heat can get pretty severe.

you will find that as roadspeed increases, the effort required to achieve and maintain the speed is higher ( higher HP/TQ requirements ).

__________________
Life is like a ride on the Freeway, Dodging bullets while your trying to find your way.

Theres more to life than only surviving.

A big question I am wondering is, does unplugging the EGR valve cause any long term damage? Maybe the turbo, or the engine, or both, were designed to breathe in hotter intake temperatures, and unplugging the EGR could effect that? I drive a 05 KW with a 450HP ISX, and I have unplugged the EGR valve for the last 6 trips. My fuel mileage has been fantastic, and it pulled much better. However, it did smoke just a hint on some shifts.

I am STILL trying to find a good truck to buy, and it seems every time I find the exact truck I want, with the exact spec I want, it has a ISX under it's hood. I have always loved CAT engines, but to me, one turbo seems more simple to work on than a 2 turbo system like the ACERTs use.

I am looking into one right now, with 900,000 KM's on it, so I guess 500,000 miles roughly. That mileage on a ISX could be scary, but I am unsure. I have heard tons of good about these engines, and some bad.

If your single turbo choice wasn't a VGT I would agree with the simplicity. However 2 normal turbos vs one with sensors and extra moving parts, I don't see a lot of difference from a maintenance or cost standpoint.

This is true. I was going to type that but I forgot. At least the CAT turbo's are just ordinary turbo's, VGT's get very expensive very fast.

The biggest factor to me would be idleing time. I think thats what turn them into ####. Thats when unbelievable amounts of soot are being circulated thru EGR, EGR coolers, tubes, liners/rings, turbos (I'm not sure if it really affects the turbo operation tho) and... oil.

Massive amounts of those "company" trucks with ISXes were constantly idled overnight for many years back. All these 670s (so cheap now!) were treated like that.

Thats something to think about, at least thats where I'm at trying to comprehend why my ISX isn't really giving me all those horrors. My idle times for reference:
4.2 % Idle at 800 rpm - rather unavoidable
5.8 % PTO Idle at 850 rpm - engine warming up, cooling down, few times used for comfort.
I dont think I could cut it further, maybe 1% ? I mean I dont idle my truck and get 10% anyway

Another factor to consider would be amount of slow/city/stop&go sort of work since it also produces more soot compared to long haul. You will never find out about it though.

Then I would go for pre-DPF 530 or 565 from 2006 - the most developed ISX (long way since 2002) before it got seriously screwed with 2007 emissions (heavier EGR + DPF filtering)

If you still don' like it, you need to go for 7 years old trucks with pre emissions engines. No easy choices here...

I have heard from Peterbilt mechanics (Turlock, CA) Accert turbos replacement is $8.000 easily

Mine, on ISX was about $2.600.

I dont see much of a CAT advantage here