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Discussion Starter #1
Deciding what to do with my truck right now.

I am fairly certain that I have a broken timing chain and thus a broken motor. It was making noise at the front. After a brief un on the freeway, it got really loud as I slowed to take the exit. Then, It just stopped dead instantly. Turning the key, the starter makes a screeching noise and doesn't really sound like it is turning the motor.

So, before I do anything, it would be nice to know if this motor is in fact hosed. I have pulled the water pump off but I can't get a clear view of the TC. Do I have to pull the HB and remove the cover to tell if the chain is broken?

Is there any other way to confirm? With a gasser I can just check the distributor. If I turn the motor over manually, the IP drive gear shouldn't rotate if the chain is broken correct?
 

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Correct, broken chain means injection pump won't turn-it could be the key broke or something else-but chances are a lot of valves hit pistons and there are some bent push rods, so at that point it's moot what actually broke.


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Discussion Starter #3
Well, it appears that the TC is fine but something else is very, very wrong.




You can see in the first video that the motor is barely moving when the starter cranks but in the second on, you can see that the flexplate and Torque Convertor are spinning.

:confuzeld



Broken Crank? When I rotate the motor by hand it feels normal and has good compression. The flexplate doesn't appear broken.
 

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Pull the front pulley, use a large socket on the front crank bolt, and slowly rotate(may help to remove glow plugs) and watch the flex plate-if it doesn't move with the front half, you need to remove the torque converter and make sure all the bolts are installed. If they are, then a broken crank is likely

Should say, it isn't necasary to drop tranny, just need to push it back.


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Discussion Starter #5
So, I found that it is the Flexplate. It is shredded right around the crank. Just didn't look carefully enough the first time.

I have two threads going, this one and one for the noise I was getting before this failure. The questions I still have are why would the flexplate failing cause the motor to instantaneously stop? And what was the noise I was getting before the flexplate broke?
 

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Could still be a broken crank-excess vibrations resonating along the crank causes it to crack-think of the flex plate like a second harmonic balancer.

Now, you'll still need to try and determine if the front and rear of the crank move with each other or if there is a lag between the front and rear indicating a separated/broken crank.

And maybe luck has it-the flex plate broke while driving, jammed up against the crank momentarily and stalled the engine...possible, but it would take quite a bit to stall the motor, so...further investigating is required.

In your other thread, I believe you said the harmonic and pulley checked out good?


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Discussion Starter #8
The front of the motor looks good and normal HB is in decent shape and everything moves as it should.

My plan as of right now, is

- Order the flexplate
- Pull the transmission back or out.
- Check the rotation of the rear of the crank when I rotate the front.
- Replace the Timing chain since I have a new one sitting here
- Replace the HB since I will have it off to do the timing chain.
- Install the Flexplate and fire it up
- If that is successful, bolt up the transmission.
 

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Might be wise to pull the transmission front pump and inspect. Does not take a lot to damage the pump. :eek: Maybe others can chime in on the pump or start a new thread on transmission.
 

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Discussion Starter #10
Hmm...if there is a transmission problem, I am just going to do a manual transmission swap. I hate this TH400. But I would like to hear anyone's thoughts on possible damage to this one.
 

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If you wasn't on the wrong side of the country...I have a perfectly good TH400 with 86,000 miles on it I just took out last week before swapping in my NV4500. Worked great...just needed another gear....an O/D.
 

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Discussion Starter #12
If you wasn't on the wrong side of the country...I have a perfectly good TH400 with 86,000 miles on it I just took out last week before swapping in my NV4500. Worked great...just needed another gear....an O/D.
It isn't actually *this* TH400, it is the TH400 in general. I don't need a heavy duty tranny but I definitely could use another gear. Exactly why I want an NV4500. Unfortunately, they are super rare out here.
 

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you might as well drop the oil pan to help in your diagnosing, you might see right away a really crooked rod, relatively easy to do in the truck.....
 

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Discussion Starter #14
you might as well drop the oil pan to help in your diagnosing, you might see right away a really crooked rod, relatively easy to do in the truck.....

But I don't wanna :bawl:

Haha. I have been trying to justify to myself not pulling it off because I hate sealing it back up in the truck. :HiHi:
 

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Discussion Starter #15
you might as well drop the oil pan to help in your diagnosing, you might see right away a really crooked rod, relatively easy to do in the truck.....
So, rods all look good and things look pretty clean - about the same as a year ago when I sealed it up.

The only thing I noticed was the #2 piston looked a little darker in the center than the others. Should I be concerned? I tried to get a pic of it but it is hard to get a clear shot so I'll have to try again tomorrow.

Got to get the center section of the flex plate out then I can start to put it all back together.
 

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If you need a flexplate give me a shout. I've got a couple! Hoping you didn't lunch a crank too! That job is no fun...

Keep at it man!
 

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Discussion Starter #17
I just had a new one show up. Took me a minute to figure out which one I needed since 82s didn't come with TH400s.

So far, crank looks good. Doing the rear main seal and replacing the oil pump while I am in there (both are fine now but I don't want to do this again) so I'll do a complete inspection then.
 

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We use to tear down race engines after a 500 mile race and inspect the bottom of the pistons. They needed to be burnt brown. If they were clean we either had the fuel mixture to rich or the engine wasn't making the power. In the case of the diesel I would just be guessing. Just one burnt on the bottom I would wonder if that cylinder is running hotter than the others.
 
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