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Replacing cracked flexplate

Kp

1/2 ton status
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Apr 5, 2006
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Tucson
Well, dodged a bullet, and the lower end knock I was hearing turned out to be a cracked flexplate, and not a rod bearing.
So now I need to replace it, but I am not sure if I can do that without splitting the engine from the tranny?
Engine is a 454, tranny is a TH400.
My Chiltons book doesnt say. Does anyone know?
 
I replace mine due to it being cracked. The easiest way is to go ahead and remove the tranny. It only takes a few more minutes than just pulling it back. Get a tranny jack, having the right tools makes the job a piece of cake.
 
bummer.
I was hoping to be able to do it with the engine and tranny together. oh well.
Any idea what causes these to crack? Its exactly 1 year old. I put a new flexplate on when I put the new engine in last February.
 
Incorrect flexplate to converter bolts, or incorrect flexplate to crank bolts?
(or both?)
Summit has one that they claim is 35 mils thicker than stock. Probably worth the extra 15 bucks huh?
 
Pioneer makes a good one. You can get them for as little as $20. For about $45 you can buy the thicker ones that are also SFI approved, but more importantly stronger. I didn't check Summit's site but it might be a PIoneer that is rebadged.
 
I think i am in the same boat.
I thought i had a rod knock, but its got to be a cracked flexplate.
I have done a couple in the past and all i did was unbolt the tranny, unhook the tranny lines, shift linkage including 4x4, crossmember , driveshaft front and rear. once everything is unbolted and disconnected, move the tranny/tcase back about 4"-5" , enough to get a ratchet in there. you should be able to remove the bolts.
good luck.

mike
 
Yep you have to split the engine from the tranny. I have never been able to do it without dropping the T-case, but maybe you have more room.

I drop the t-Case and then I put 4 long bolts like 8 inches in place of the bottom 4 bolts that hold the tranny to the motor, then take out all the other bolts and with the tranny supported by a jack I slide the tranny back on the shank of the bolts, replace the flexplate and slide the tranny back in place. Keeps everything lined up and makes it a little quicker.

If you havent done a tranny fluid and filter change it might be a good time to do that.
 
Too late now to get one from Summit before Sunday. I'll check the local hot rod shops and see if they have one thats not too steep.
 

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