TH400 to 5.3 issue
Thread Starter
Joined: Nov 2009
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From: THORNTON, PA (NEAR PHILLY)
TH400 to 5.3 issue I have a TH400 with a LS Ultra Bell installed, and reusing a 10" ATI sbc/bbc converter. As I u/s it when using a 4l60e "dished" flexplate, you need to use the GM spacer bolted on the trans side of the flexplate - which I did. The problem is that the converter has almost no freeplay back and forth - like maybe a 1/16" or less. The converter does spin freely though. Its like the crank spacer is too thick. If I get the 4l80e flex/spacer, I think I will gain the thickness of the flexplate (1/8"??). Is an ~1/8" enough freeplay for a converter? Currently the converter mounting pads are about 3/8" away from contacting the flex.
That should be fine. Mine sat a bit off the flexplate as well. As long as it is not binding up, you said it turns freely (converter), you should be ok. Remember, the purpose of that spacer is to support the snout of the converter because it is not made long like the newer stuff is. Once you get it bolted down, you should be just fine. Mine sat a bit off also. I did not use any spacers for the bolts and my truck started just perfect every time. No damage to starter or flywheel of any kind. But if you can, tighten them up a little at a time to avoid binding. I know its a pain, but it avoids binding the snout and converter crooked causing pressure on the trans pump.
Thread Starter
Joined: Nov 2009
Posts: 1,621
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From: THORNTON, PA (NEAR PHILLY)
That should be fine. Mine sat a bit off the flexplate as well. As long as it is not binding up, you said it turns freely (converter), you should be ok. Remember, the purpose of that spacer is to support the snout of the converter because it is not made long like the newer stuff is. Once you get it bolted down, you should be just fine. Mine sat a bit off also. I did not use any spacers for the bolts and my truck started just perfect every time. No damage to starter or flywheel of any kind. But if you can, tighten them up a little at a time to avoid binding. I know its a pain, but it avoids binding the snout and converter crooked causing pressure on the trans pump.
I'm not worried so much about the converter mounting pads being off the flex so much as I'm worried about the lack of lateral clearance/movement. What if the crank as some back/forth play? That could surely cause an issue as could things swelling up once they get to operating temp.
Then it has met a stopping point for the lateral movement. Help keep things stable.
As far as once it warms up, I don't think it'll warm up that much. But, that's me. If you want to pull it apart and get it turned down a little bit that's your call, but I would not go more than .050-.060 which would barely give you more room, but not compromise the support of the converter.
As far as once it warms up, I don't think it'll warm up that much. But, that's me. If you want to pull it apart and get it turned down a little bit that's your call, but I would not go more than .050-.060 which would barely give you more room, but not compromise the support of the converter.
TECH Regular
Joined: Oct 2011
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Looks to me like you have things out of order
when useing an older style trany and converter to an ls engine
1 if using a dished flexplate the order is, engine-flexplate-spacer
2 if using a flat flexplate the order is, engine-spacer-flexplate
when useing an older style trany and converter to an ls engine
1 if using a dished flexplate the order is, engine-flexplate-spacer
2 if using a flat flexplate the order is, engine-spacer-flexplate
Thread Starter
Joined: Nov 2009
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From: THORNTON, PA (NEAR PHILLY)
This is a 5.3 with the dished flex on first, then the spacer.
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Verdad Gallardo Thread Starter
Joined: Nov 2009
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From: THORNTON, PA (NEAR PHILLY)
I did a search and found a thread or two that states sometimes when using the spacer you end up with clearance a little too tight and the spacer needs to be machined down a touch. By me using the the 4l80e/flat flex setup (spacer bolting to the crank then flex) will free-up another 1/8" or so (whatever the thickness of the flex is). That should be enough clearance I believe. Easy enough to do.
I don't think it will matter. The flexplates are the same thickness for automatics. So regardless of whether you use flat or dished, its gonna be the same on the snout of the converter.
Thread Starter
Joined: Nov 2009
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From: THORNTON, PA (NEAR PHILLY)
OK, went to Autozone and bought Pioneer flywheel FRA-450 which is a 4l80e and bam! Fits like a glove! I didn't even need to enlarge the flexplate bolts - a direct bolt-in. If anybody wants to attach a th350/400 converter to a LS engine this is the plate to use for only $65.00
Converter moves back and forth a nice .144". Should I shim it a bit tighter or run the sucker?
Converter moves back and forth a nice .144". Should I shim it a bit tighter or run the sucker?
I also have a TH400 with an ultrabell on my 5.3, but I used the TCI flexplate for the SFI cert. Just a bit more than $65. 
With the TCI, there is no spacer, just a pilot adapter for the converter hub. It basically floats in there.
Anyway, I also ended up at .144" of space from the conv to the pads, so I added .060" washers. Although I think it would have been just fine without them.
Ron
With the TCI, there is no spacer, just a pilot adapter for the converter hub. It basically floats in there.
Anyway, I also ended up at .144" of space from the conv to the pads, so I added .060" washers. Although I think it would have been just fine without them.
Ron
