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Discussion Starter #1
So I am changing the clutch/pressure plate in my truck. I noticed that there was a broken spring in the dual mass flywheel, so since I had one from an exact same truck that only had a little use before the truck died, I decided to use it. Then I discovered that the 7.3 engine used two very different flywheels, at least where the pressure plate mounts. Things being a little tight right now, I decided to swap the outer plate of the flywheel with the one that I had pulled off. It fits, bolts up right, rocks like it should, and looks like it belongs there. Before I stab the transmission, since what I did isn't a common practice, I need to know: Does anyone know of a reason this won't work. While I would like to save a little money, I also don't want to break a crankshaft either.
 

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What! 120 of y'all have looked at this, and I don't even get a smart-ass remark
 

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Are you sure that you didn't put the spring in backwards or upside down?
 

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Discussion Starter #4
No springs ever came out other than the broken one. I know it was broke because it was in two pieces. I saw that before I ever took anything apart. The reason I wasn't going to use the old flywheel. As far as difference, it was the bolt pattern on the clutch plate of the replacement that wouldn't match up with the pressure plate, internal parts all looked the same. I swapped clutch plates, all of the springs stayed caged where they belonged, never moved. I made sure that nothing moved while I was replacing the clutch plate (mostly because I didn't feel like eating flying springs). I used the base of the replacement, and the clutch plate from the original. Torqued all of the bolts down to 50 LBS/FT, with blue locktite, crankshaft, and clutch plate bolts
 

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You say exact same truck, but to be sure were they both non turbos? The balance is different between NA and turbo. Can't interchange.
Otherwise, I'd say go for it.
 

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What! 120 of y'all have looked at this, and I don't even get a smart-ass remark
Personally, I've never had mine apart. And it appears to be a mysterious "dead spot" when it comes to any information on the dual mass flywheel ass'y in IDI shop manuals. I've got a FoMoCo 7.3 engine and trans, etc, manuals plus a Navistar 7.3 engine manual and no mention or even a pic in any of them.
 

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Discussion Starter #7
You say exact same truck, but to be sure were they both non turbos? The balance is different between NA and turbo. Can't interchange.
Otherwise, I'd say go for it.
Both non turbo.
Based on what everyone said, I'm going to run it. I'll post updates when and if something happens
 

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Discussion Starter #8
The balance is different between NA and turbo. Can't interchange

It has just occurred to me, that they put turbochargers on non-turbo engines all of the time, but I have never heard of anyone ever changing the flywheel, nor have I ever heard of any damage because of that.
 

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For some reason that doesn't make any sense since they are basically the same engine.

For LMJD perhaps the reason that the manuals don't speak of repairing them is that the flywheel is considered a one time use only and not intended to be rebuilt.

Hope it works out for you
 

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The balance is different between NA and turbo. Can't interchange
It has just occurred to me, that they put turbochargers on non-turbo engines all of the time, but I have never heard of anyone ever changing the flywheel, nor have I ever heard of any damage because of that.
You are absolutely right, I installed my ATS kit at 30,000 miles on my non-turboed '91, got 249,000 on it now and never touched the flywheel, clutch, and no engine or clutch vibration. Back in the day when these IDI's were fairly new and installing aftermarket turbo kits was REAL common with a lot of members here, there was never any mention of a balance problem. Like some other forum "revelations", probably something somebody dreamed up to sound more knowledgeable than the next guy. Plus after all these years I've still got my ATS installation instructions which are real complete and informative and there's no mention there either of a balance problem.
 
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Discussion Starter #11
For some reason that doesn't make any sense since they are basically the same engine.

For LMJD perhaps the reason that the manuals don't speak of repairing them is that the flywheel is considered a one time use only and not intended to be rebuilt.

Hope it works out for you
Trust me if ANYTHING doesn't look or feel right, it WILL be coming right back off. I've rebuilt many engines, and seen quite a few strange things, besides the one 7.3 broke crankshaft I already had because of a failed flywheel (that one just flat wore out). Just saying I know what flywheel vibration feels and sounds like. This is just a get-by until I can rebuild an engine to put in this truck anyway, but I want to get by until I'm ready to change it out.
 

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I guess I wasn't clear enough. I was referring to factory turbo's vs NA. The engine internals are different on the turbo engine, different balance from the NA. The factory turbo's flywheel has a different balance. Turbo itself makes no difference, and I've never heard anyone say that. Hope that helps.
 

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I guess I wasn't clear enough. I was referring to factory turbo's vs NA
That's what we're referring to. Most of us are aware of the internal differences of the factory turboed engines, Keystone rings, larger wrist pins, etc. However, hundreds of us have installed aftermarket ATS, Banks, and Hypermax turbo kits on our factory non-turboed pickups over the years with original non-turboed flywheels and there's no problems whatsoever after doing so, balance wise or otherwise.
 

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Discussion Starter #14
It made smoke today. No abnormal vibrations, or unusual noises. I have discovered that I am getting entirely too old to be doing that sort of thing. I think I'll leave that for those young bucks who think nothing of bench pressing a transmission. Still can't drive it yet, bleeding the clutch, and while I was in there, I must have knocked something loose under the dash, no start from in the cab. I also replaced the power brake booster, so there is bleeding the brakes too.
 

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I have found that with age comes wisdom.

I have found a great mechanic and he loves working on OBS trucks with the 7.3 in them. He was a dealer mechanic before he opened up his own shop.

I have also learned that I am beyond muscling a transmission up and back into place not to mention pulling it out. I have also found that I like the skin on my knuckles and clean fingernails. Not to mention that I don't need anymore tools than I already have. So when a job comes up that I just don't want to do I take my truck down to the mechanic shop and let him have at it.

I then load up my other vehicle and go fishing.
 
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Discussion Starter #16
Well after a couple of hours looking at wiring diagrams, crawling around under it and bleeding everything, I finally drove it down the road about a mile. everything seems to be normal, so I'll trust it to go to the nearest town and back. About 20 miles, after that, I might trust it to take me to work and back, about 80 miles.
 
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I then load up my other vehicle and go fishing. So when a job comes up that I just don't want to do I take my truck down to the mechanic shop and let him have at it.
I like the way you think! :grin2:
All kidding aside, even when I was young, I'd sure rent a trans jack to pull a ZF sized trans. Air conditioning work has never been one of my main events, so I'm going to take my '91 to a shop in a couple months, have the original freon converted to R135 or whatever it is, plus I noticed my compressor front seal is leaking freon.
 

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I like the way you think! :grin2:
All kidding aside, even when I was young, I'd sure rent a trans jack to pull a ZF sized trans. Air conditioning work has never been one of my main events, so I'm going to take my '91 to a shop in a couple months, have the original freon converted to R135 or whatever it is, plus I noticed my compressor front seal is leaking freon.[/QUOTE

Trust me I had a transmission jack. Still had to do a little bench pressing
 
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