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Discussion Starter #1 (Edited)
When I was installing my new converter last summer, I noticed it was very tight going on. When I called the builder, I was told that it was normal for their converters to fit tight. I checked the splines of the input to make sure they were damaged, burred, or twisted. All was good, so I went with it. After installation, the conv still never moved freely on the spline. Against my better judgement, and the fact I was in a hurry to get ready for a race, I said screw it.

Well, only after a few races ( 2 months ), we found that the thrust main had cracked in the block. this was a fresh build and no damage was found during assembly. During tear down, we had a hell of a time pulling the converter off the back of the crank. So much so that the hub got damaged pretty bad.

There is additional things we found wrong with the shortblock assembly that could have contributed to this failure as well. But, my question for this forum is, is it possible that the converter fitting too tight on the input could have been the cause of the block failure?

Any input would be appreciated

Thanks
 

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if the turbine in the converter was stuck to the input shaft and you drew in the bolts from the converter to flexplate you could have removed all the end play and caused the failure.depending on which way it moved or didnt move during tightening will dictate which side of the thrust bearing gets eaten for lunch.
 

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Discussion Starter #4
The converter moved a 1/8", but I had to use a pry bar to move it forward.

Fwiw, the converter is currently back at my converter guy getting repaired and adjusted for my new motor. The issue of "tight fitting spline" is being addressed.
 

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The entire process of installation doesn't sound good. Typically , if you have to get out the heavy tools to do a converter install or if the job is in any way fighing you , there is a problem. Tough to say what really caused the engine problem but I would say the tight fit didn't help it at all.


Hutch
 

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the o.p. EXACT WORDS WERE..had to pry the converter off of the crank..

well,
as you know, the PILOT is suppose to be slip in loose into the hole in back of crank...

so,
issue number one...

second thing, his opening post states that the "converter is tight on input shaft.".. well, issue number two..
the converter is not suppose to be tight..it MUST FLOAT...otherwise the forces will push all forewards and then add to issue number one...
actually it probably was not tight on input shaft, but rather could have been tight on the large slotted drive tang.....

issue number three..
there are numerious input shafts designed and specifically made to fit ONLY CERTAIN converters...( hubs too) because of each makers different diameters...the amount of oil that can or cannot pass around the shaft....can damage the trans assy because it aint allowing oil to flow with pressure out into the converter...
there is also a related post topic about a ringless shaft in this posting area... read it to understand....
 

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the o.p. EXACT WORDS WERE..had to pry the converter off of the crank..

well,
as you know, the PILOT is suppose to be slip in loose into the hole in back of crank...

so,
issue number one...

second thing, his opening post states that the "converter is tight on input shaft.".. well, issue number two..
the converter is not suppose to be tight..it MUST FLOAT...otherwise the forces will push all forewards and then add to issue number one...
actually it probably was not tight on input shaft, but rather could have been tight on the large slotted drive tang.....

issue number three..
there are numerious input shafts designed and specifically made to fit ONLY CERTAIN converters...( hubs too) because of each makers different diameters...the amount of oil that can or cannot pass around the shaft....can damage the trans assy because it aint allowing oil to flow with pressure out into the converter...
there is also a related post topic about a ringless shaft in this posting area... read it to understand....
Part of this is correct. The pilot should not bind in the crank. The conveter should not bind on the shaft. There are not specific shafts for converters besides the ones built for oversize shafts and you'll not be able to mix and match those at all... not even close to fitting one another.
 

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Discussion Starter #8
I had multiple problems with my last combo, the converter was just one of them. Ultimately, I don't believe the converter was the main culprit, certainly not good.

The main issue, that's being discussed in the NA forum , is that my crank had zero endplay.

I appreciate everyones replies, thank you.
 

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BUT,
when the converter pilot nose is STUCK in the crank..
the forces from internal oil pressuer from transmission can and will exert force on the crank....

the pilot nose MUST be free and loose to FLOAT...
 

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BUT,
when the converter pilot nose is STUCK in the crank..
the forces from internal oil pressuer from transmission can and will exert force on the crank....

the pilot nose MUST be free and loose to FLOAT...
agreed, just like bottoming it out in the crank. hutch has a cool video of how much it moves.
 

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Discussion Starter #11
BUT,
when the converter pilot nose is STUCK in the crank..
the forces from internal oil pressuer from transmission can and will exert force on the crank....

the pilot nose MUST be free and loose to FLOAT...
When the converter was first being installed, the pilot fit freely into the crank. It wasn't until after the block failure was discovered that I found that the converter pilot had become bound/siezes into the back of the crank. So much so, that my buddy and I spent a good hour and a 1/2 with pry bars trying to get it loose until it finally came off.
 

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If you had to pry the converter towards the flexplate to get it in and it pushed whatever thrust you had in the crank forward and the converter couldnt slide in and out on the input shaft itll kill the thrust bearing.the crank converter and flexplate are 1 unit when bolted together and must be able to move in and out on the input shaft an amount greater than the crankshaft endplay or guess what happens?
 

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BUT,
when the converter pilot nose is STUCK in the crank..
the forces from internal oil pressuer from transmission can and will exert force on the crank....

the pilot nose MUST be free and loose to FLOAT...
Not if you have a quality torque converter. There should be NO flexing of the front cover at all. Especially if it has a cast or billet cover. As stated, they should be moving as an assembly if at all.
 

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Discussion Starter #15
With all this said. The converter to crank pilot needs to be and stay free inside the crank so when the flexplate flexes , it is allowed to move in and out with ease. The same goes for the splines.

As seen in this video. http://www.youtube.com/watch?v=YEfqKoilLkI


Hutch

WOW! Thanks for the vid Hutch. I had no idea the converter/crank assembly moved that much. I'll definitely keep this in mind from now on.

Thanks again!
 

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I just bought a new C4 converter because my old one had internal cracks in it. Went to install it and I could not get the converter to seat correctly. I pulled the input shaft out and tried to put it into the TC and it was very tight, I could pick the converter up by he input shaft. It was very hard to get out. I ordered a PA input shaft thinking my input shaft was damaged the new on was just as tight. I managed to get the TC seated With the new shaft but once seated it will not move forward. You have to jerk on the TC to pull it out. I'm thinking is the converter. What do you guys think. Thanks Jason
 
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