I'm buying an old uhaul, it's an 88 International s1600. Non turbo, pretty sure it's a 7.3 IDI motor. I'm not a fan of diesels, and I've never really worked on them. So my question is what parts should I be planning on having to rebuild on a 240k mile truck? I'm sure runaways aren't a common thing but what should I look at on this thing to make sure it won't? It's been sitting for probably a year but supposedly has always run fine. The thing also needs a clutch, I haven't pulled the trans yet but it's probably a dual mass flywheel. What are decent inexpensive brands for a flywheel and pressure plate / clutch kit? Most that I've found are solid flywheel swap kits, which I don't want.
How good is the 7.3 diesel vs swapping it for a 460? It's a 24' box truck that I'll be hauling my race car in.

 

Solid flywheels may make more noise but are less likely to fail than dual mass. Most of us prefer smf over dmf. I suggest luk. They tend to hold up the best from what i have heard, and also be very cost effective. Thats what I would put in my truck.
Injection pump and injectors tend to wear out as a set around the 80-120k mile mark. Check out how it cold and hot starts, how it runs, and what smoke looks like. That will give a fair indication of how the pump and injectors are doing.
Honestly I would simply check it over like any vehicle. and replace what needs replacing, or gives problems. Biggest thing is buy quality parts. Motorcraft, or idiperformance.com will pretty much be all ya need.
Check fluids change what is needed. I like to start fresh on any of my vehicles, whether that be timing belts, spark plugs, or injectors and injection pumps. I start at the front and work back changing fluids and whatever else shows signs of failing. It should do alright. It is a work horse designed to just work. It is not fast but will get the job done. it should get better mpg than the 460, but that is also a lot of truck. Hills will be slow. but fuel eco will suck on a 460. Turbo seriously helps an idi.

 

That should have the eaton 5 or 7 speed and SAE bell housing, which should already have the single mass flywheel. Ive never seen one with even half the synchros intact though. I would check which transmission you have (if you dont already know for sure) and probably get ahold of international for the clutch if its the eaton.
Never personally heard of or seen an IDI run away, but there is a vid of one on youtube. Really only way i can forsee a runaway is a turbo seal failing. Find a used turbo kit and shoehorn in there, or you can buy a new one from hypermax i think, for the S series. The 7.3 is a great engine, they tow well and get decent mileage. With even a used turbo and the fuel turned up a bit it will easily out tow a stock 460. We have an 84 S1400 with the 6.9 and 5+2, it actually moves surprisingly well for being 19k and even gets about 11 mpg with the 4.88 gears (and 10R 20s) the 2spd is blown, so it tops out at 58mph. You wont win any races with it NA, but it will do it. If its fresh from uhaul, they took pretty good care of their IDI fleet, so you might have gotten a pretty good deal. Sitting wont have hurt it any. Biggest issues with the IDI are minor, and all covered in the stickies at the top.

 

It's a 5 speed trans, not sure what it is yet.
It's N/A so I doubt there's much of a chance of a runaway, but I wasn't sure how prone the injection pumps are to sticking or anything like that. It's only been sitting for about a year, maybe year and a half. I'm buying it from my boss who only used it for storage after driving it home. He got it from an equipment sales place. So I doubt it's been used since uhaul got rid of it. There's a tag on the back of the cab for tracking maintenance, and the 240k mile spot has sticker residue on it. It has only a hair over 240k on it now. I could probably sell the motor for what I paid for the whole thing so I'm not concerned about the condition from a financial standpoint. I'll definitely pull the trans and see what the clutch is before ordering anything, I've heard it both ways now solid vs dual mass. I'm not going to do anything to the motor, if it runs then it's plenty good for me. If I'm going to boost something I'd rather spend the time and money fitting a blower on the race car Thanks for the responses, now to pick up a couple batteries for this beast...

 

If it's a spicer five speed don't sweat the syncro issues, they float like a dream when you put 85-140 in them!

How clean is the engine? If it's painted orange it's been overhauled before by uhaul

 

Duh, spicer, not eaton, i knew it didnt sound right.

 

If it does happen to have a DMF, you ABSOLUTELY want to swap it for a SMF.
I've taken two DMFs out of my two OBS fords within the last year. The first one I did, in my '92... it would barely hit 60 without slipping with very light throttle. Tear it apart, and the clutch disk looks OK. I didn't think much of it, figured maby the pressure plate wasn't holding well.
The DMF was also, well, falling apart. The ball bearings that it was riding on were literally falling out.
Do a full SMF swap and away I go.

My '93, on the other hand, wasn't doing too badly. It was fine when I got it, but on a 3 hour trip to pick up the '92, it started slipping when I floored it. I carefully made it there and back, and cold it was fine. If I'd actually get it hot, though... it'd slip.

For this one, I just bought a DMF clutch disk and pressure plate. I figured it would be an easy fix. Pull the trans, get in there... clutch disk looks OK. WTF?
This DMF didn't look bad. It had a Valeo sticker on it from only a few years ago.
I swap over the new pressure plate, put it together and... still slips.

That's when I learn about the /real/ problem with the DMF: The "torque limiter" clutch. Inside the flywheel there is a strip of friction material about 1" wide by perhaps 8" in diameter. Bolts and springs hold the flywheel bits against that strip(so there's a decent amount of pressure)... but the entire output of the motor goes through that strip.
Over time, as you exceed the "limit" of that, it wears down. And that's at near-stock power levels, not what you want if you actually intend to *use* the truck for hauling.

I just mig-welded the two halves of the DMF together, and hey - problem solved!
'Course, it was /really/ noisy(with no damping really), but no more slipping!

I then got a LuK SMF kit, swapped it in, and have been using that ever since. Very nice clutch, softer pedal than stock, has a lot of springs in it, and holds plenty of HP. I haven't had any trouble with it slipping, period... and I'm nowhere near stock power levels.