A guy I know has a F350 With a n/a 7.3L 5spd. he put in a new clutch, "it was not the right one" (Im told.) eng./trans made bad noise. his dad says he broke the crank...is that possable??? due to wrong clutch??? DAVE S. you said you broke a crank in '05? what was the symptoms (Iknow, that sounds stupid) -- AND what was the worst damage that anyone has done to the IDI and what was the first clue that somthing was going wrong. be descriptive COME ON GUYS DONT BE BASHFUL YOU CAN TELL US.

 

I was about to say I've never heard of an IDI with a broken crank and then you say Dave S. broke one. I've SEEN a broken Duramax crank and pictures of two others though.

Did he break the crank "internally" or back on the flange when installing the clutch? Since it "made bad noises" I'm assuming it was internal. Just curious.

Here's my irnorance shinning through: could it be the "dual mass flywheel" I've HEARD of them "coming apart" and making noise. I barely understand what a dual mass flywheel is but it sounds like a bad idea to me, from what little I know.

 

I've never heard of a broken crank on a 6.9/7.3 IDI either. I'd like to know how you can even break a crank like that. Its MASSIVE!!!! I would guess it weighs close to 100lbs worth of forged steel.

As for the DMF, its was a bad idea. Ford and GM used it in their diesels in the early 1990s and late 80s, dodge never did to my understanding. Think if it like pushing one truck with another with a big spring between them instead of bumper to bumper. The sole purpose was to make the truck run smoother and reduce gear clatter at idle. Officially it was to"prevent damage" to the gears of the transmission, but ford and GM have both since abandoned the DMF, and the springs are back where they should be in the clutch disk.

I did a SMF conversion on a 1995 ford powrestroke recently. The DMF basically exploded and fragments of spring were getting thown around in the bell housing. Some had jambed between the flywheel and the engine causing a loud tinny scraping noise. DMF is one of the worst ideas ever........

 

Dodge Cummins..

Dual-mass Flywheel
The dual-mass flywheel absorbs engine vibrations before they are transmitted to the driveline where they can create gear rattle. A dual-mass flywheel is split into two sections: a primary section that bolts to the crankshaft, and a secondary section, onto which the clutch is bolted. The primary section of the flywheel contains springs to isolate engine vibrations and a torque limiter to prevent engine torque spikes from exceeding engine and transmission component strength. When torque spikes occur, the torque limiter allows the primary section of the flywheel to turn independently of the secondary section, preventing damage to the driveline and transmission.


Dual Mass Flywheel

 

If you install a clutch plate with a larger splined socket (not correct match) you will hear the input shaft of the transmission strip and make a terrible noise. Can it be started? Because the starter turns the flywheel, which is connected to the crankshaft. I guess they could have over-tourgued the flywheel bolts either on the crank, or the pressure plate.

 

I was told that it made a bad niose...the guys dad told him he had a broken crank..to much end play on the crank..how much?? I dont know... its torn all apart now..I was wondering how much it was worth...F350 4X4 5spd 4 door...miles??? I dont know how manny...(well I gotta go I got a call about some hey...Ill try to grt back on tonight)....I was hoping that DaveS. would give me some help...

 

Guys, cranks break. I have replaced a few in various motors. Bad machine work can cause one to break in a heartbeat. Example is turning a journal and not making sure the fillet is cut. The fillet Is the corner wear the bearing journal comes off of a web. A radius needs to be cut there. Same with cams ect.

It could have been a bad crank. Typically you don't see it near as much in a diesel crank because of the steel they are generally made from.

I would have to go look but I don't think these cranks are billet cranks so it is easy to have a bad casting.

I have replaced a couple 3406 Cat cranks. They had some crank problems awhile back. Allot of these cranks were lasting 1/2 million miles.

I have a crank out of an N-14 that cracked and was caught during an in-frame. I have it at home. Will be a Mail box post.

Another thing. If you see a crank broke in a motor make sure you have that block checked GOOD. You could have a block problem that put a side load on the crank. Meaning the main bearing bore got out of wack.

 

The broken crank was in one of my Reviva reman 7.3 turbo engines.
From day one, it had a funny feel, almost like a vibration.
It also had a very funny sounds to it.
Oil pressure was always very low as soon as it was warm.

If I remember right, I got 9700 miles out of that engine from the time I installed it.
The longer I drove it, the worse the now definite vibration got.
The last day I was working 50 interstate miles north of town.
On my way home, the vibration was so bad, I got off the interstate so I could drive slower on the back roads.
Then the clutch started acting funny, not wanting to engage.

I did not make it home that evening.
I did get back to town, and there was this big bang when I went to pull off from a stop sign.
Engine running, but really shaking.
Turn engine off, start engine, still shaking and the starter really sounded funny when it engaged.

Tow to shop, remove dust cover from bell housing.
Flywheel was not parallel with the back of the engine.

During tear down,when the transmission was removed, the flywheel fell on the floor.
The break was in the rear main bearing journal at about a 50 degree angle to the bearing surface.

That little episode also took the input shaft bearings out of my T 19.

Even though I was mad, I was impressed.
The crank was broken into two pieces, but it still started and ran.
I never did take the oil pan off, but I bet the rods were in bad shape for the two rear cylinders.

My guess is the crank was cracked and Reviva never caught it when they rebuilt the engine.
Under the right conditions, a hydrolock can break or crack even that massive crankshaft.
I have seen bigger ones (like you can't even pick it up bigger) broken that way.

 

i broke a crank in a 1693 cat

 

Thats an oldie.

 

yeah.we were poor and couldnt afford new so we jus went with it.but i did like that truck,1972 pete,1693 cat my uncle turned waaay up,5-speed main box 3-speed auxillary,and a 39" all steel fruehoff frameless dump trailer.i really did like that truck,i learned to drive in it when i was 12 years old.

 

Then you would remember the KT series Cummins. They are big motors for a truck. High HP but no torque.

I got to drive the CFI T-2000 that broke the land speed record a few years back. It was at the Truck Show in Louisville one year and it stayed at the dealer I worked at for a few days. We drove it around the parking lot. It had a KT in it.

 

kt 600 our neighbor had one in a ih dumptruck,WOW.

 

One of the Duramax cranks I saw pictures of was running perfectly with the crank broken in two, at an angle in one of the mainbearings. They only noticed it when they tore it down to "hop it up".
I also had a friend who had an injector in his '97 Powerstroke leak and he hydrolocked it when he started it. It didn't break the crank but it bent a rod pretty good. It still ran it just puked a lot of white smoke out of the exhaust. He had to find an "old" experienced diesel machanic to figure it out.
The dealer's "computer scanners" tried everything to fix it but since the computer couldn't tell them the problem they threw parts at it until they ran out of things to replace.

That's basically what I thought the dual-mass meant, it's kind of self-explanitory. Doesn't seem like a good idea in a H.D. pick-up. I get the drivetrain shock thing but clutch springs seem to have basically worked for a long time. Plus you change the clutch, you change the springs. Keep your flywhell just surface it. The "old" way makes more sense to me.

 

i think a twin disc clutch like a semi would be better than a dual mass flyweel.but i'm no engineer.