Bent crankshaft, what could have caused it?

97White'nSilver · Aug 24, 2016

I had my truck swapped from an auto to a manual at a local shop and when I got it back it was very loud and the truck shook quite a bit. The owner of the shop told me this was normal because of the single-mass flywheel I added so I went with it. This week after about 2000 miles on the swap I started a vacation to Oregon from montana. About 10 hours in we pulled into a gas station and the truck was covered in oil. It was about 2qts low and leaking from the rear main seal and I was an hour from a friend that I could take it to. At this point the starter needed to be hit with a wrench to start the truck and the usual rattling from the trans was louder so I limped it at 35 to the house and left it for the night. It was towed to a local shop my friend recommended and they drop the trans found dirty fluid with metal flakes, the pilot and throw out bearings were exploded and the rear main seal was destroyed. The flywheel was wobbling at idleast so with the trans out the shop bolted a new flywheel on and the wobbling continued making them think the crankshaft is bent.
Tldr: auto to manual swap done by shop, truck was louder on return but shop said was normal, 2500 miles after swap rear main let go and the crankshaft is bent.

What I want to know is what could have caused this, given that I am well under 300hp and haven't been railing on the truck that hard, no sled pulls or drag racing.

78f100 · Aug 24, 2016

I highly doubt the crankshaft is bent, but I would bet money something was out of balance and got the main bearings. That is most likely why the crank is wobbling.

97White'nSilver · Aug 24, 2016

Is there anyway to check that without dropping the motor? And could a pressure plate not being torqued down correctly cause the main bearings to go out? I ask because a friend who is a mechanic thought that might be the cause of the rattling.

superpsd · Aug 24, 2016

Sucks man. What RPms does it rattle. I have the Valair ceramic as well. At idle and lugging below 1200 Roma it has a little bit of a rackety gear rollover and groan which is normal. How loud was it?

97White'nSilver · Aug 25, 2016

Before it broke it would vibrate at all rpms, the rollover and groan was low rpm but on the freeway doing 80 at 27-2900 rpm it wold rattle like crazy now it sounds like the gear rollover at all rpms but louder.

97White'nSilver · Aug 25, 2016

It's always been louder than was normal I believe because my same mechanic friend heard it for the first time and couldn't believe how loud it was but at that point it was quieter than when I first picked it up

AirFishAutomotive · Aug 25, 2016

Don't they use different spacers on rear of those

97White'nSilver · Aug 25, 2016

On the rear of the trans?

AirFishAutomotive · Aug 25, 2016

97White'nSilver said:
On the rear of the trans?

between crank and flywheel? maybe not just thought something was different about them

golfer · Aug 25, 2016

flywheel 180 out when installed.

dollars
to
doughnuts

97White'nSilver · Aug 25, 2016

golfer said:
flywheel 180 out when installed.

dollars
to
doughnuts

Do you mean it was installed backwards?

sootie · Aug 25, 2016

97White'nSilver said:
Do you mean it was installed backwards?

no, he means it was installed 180* out.

rusty1161 · Aug 25, 2016

97White'nSilver said:
Do you mean it was installed backwards?

180* off in rotation.

97White'nSilver · Aug 25, 2016

Gotcha thanks for the the explanation and yeah I wouldn't be surprised I'll ask the shop it's at now if they noticed it

old man dave · Aug 25, 2016

AirFishAutomotive said:
between crank and flywheel? maybe not just thought something was different about them

There is a spacer on the auto flexplate to make up for the difference in thickness between the flywheel and flexplate.

I don't know what the flywheel has as a spacer if any.

old man dave · Aug 25, 2016

rusty1161 said:
180* off in rotation.

Aren't the holes somewhat offset to prevent this?

rusty1161 · Aug 25, 2016

old man dave said:
Aren't the holes somewhat offset to prevent this?

You are correct, it is keyed I believe.

Rusty

golfer · Aug 26, 2016

rusty1161 said:
You are correct, it is keyed I believe.

Rusty

not keyed, but there is a rollpin, that we've seen removed and not reinstalled by others...

gwunter · Sep 1, 2016

Perhaps broken crankshaft is the problem.....but let's think positive.....if there is a positive in this situation.

Swaan · Sep 1, 2016

Id like to know the out come but im willing to bet a broken crank.
Very rare to bend a crank, let alone bend one so much it wobbles. But a broken crank will wobble and shake and make a hell of a racket just like his is doing.