Replacing Flex-plate. How tough?
Thread Starter
Instructor
Joined: Oct 2005
Posts: 113
Likes: 0
From: Melville, Long Island NY
Replacing Flex-plate. How tough?
The flex-plate teeth on my 79 are chewed up and I think I may need to replace it.
Was wondering if there are any suggestions how best to tackle this? Will this require the THM-350 to be dropped?
Also, any suggestions on a replacement part, OEM vs. aftermarket?
Thanks much. Tom
Was wondering if there are any suggestions how best to tackle this? Will this require the THM-350 to be dropped?
Also, any suggestions on a replacement part, OEM vs. aftermarket?
Thanks much. Tom
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Trans will have to come out with torque converter seated in trans(otherwise, there is no way to get to the bolts on the crank flange).
It's not a tough job once the trans is out -but getting the trans out...whew! Prepare yourself for a weekend at least of some heavy labor. Now is obviously the time you want to consider a "while I'm at it" and forecast on whether or not you want to upgrade the converter. Also may not be a bad idea to replace the trans seals if they are the originals.
You need an SFI flexplate only if you are going to be index racing to pass tech. It's a worthwhile upgrade in some cases but if you're not racing it and you're not hard on the car, you have nothing to gain. It's not like there's a huge price difference between the stocker and an SFI plate anyway.
It's not a tough job once the trans is out -but getting the trans out...whew! Prepare yourself for a weekend at least of some heavy labor. Now is obviously the time you want to consider a "while I'm at it" and forecast on whether or not you want to upgrade the converter. Also may not be a bad idea to replace the trans seals if they are the originals.
You need an SFI flexplate only if you are going to be index racing to pass tech. It's a worthwhile upgrade in some cases but if you're not racing it and you're not hard on the car, you have nothing to gain. It's not like there's a huge price difference between the stocker and an SFI plate anyway.
Thread Starter
Instructor
Joined: Oct 2005
Posts: 113
Likes: 0
From: Melville, Long Island NY
Originally Posted by gerry72
Trans will have to come out with torque converter seated in trans(otherwise, there is no way to get to the bolts on the crank flange).
It's not a tough job once the trans is out -but getting the trans out...whew! Prepare yourself for a weekend at least of some heavy labor. Now is obviously the time you want to consider a "while I'm at it" and forecast on whether or not you want to upgrade the converter. Also may not be a bad idea to replace the trans seals if they are the originals.
You need an SFI flexplate only if you are going to be index racing to pass tech. It's a worthwhile upgrade in some cases but if you're not racing it and you're not hard on the car, you have nothing to gain. It's not like there's a huge price difference between the stocker and an SFI plate anyway.
It's not a tough job once the trans is out -but getting the trans out...whew! Prepare yourself for a weekend at least of some heavy labor. Now is obviously the time you want to consider a "while I'm at it" and forecast on whether or not you want to upgrade the converter. Also may not be a bad idea to replace the trans seals if they are the originals.
You need an SFI flexplate only if you are going to be index racing to pass tech. It's a worthwhile upgrade in some cases but if you're not racing it and you're not hard on the car, you have nothing to gain. It's not like there's a huge price difference between the stocker and an SFI plate anyway.
Is there anything I need to be mindful of as far as marking things for reinstallation so I don't mess up the balance and cause a vibration? Or is each component balanced on it's own?
Thanks, Tom
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by TPL79
Jerry, it's been 16 years since I had the motor and tranny out and I have forgotten the process. If I recall, I must first remove the bolts attaching the flex plate to the converter? When I pull the trans, the converter will come out with it, flex plate stays bolted to the crank flange?
Is there anything I need to be mindful of as far as marking things for reinstallation so I don't mess up the balance and cause a vibration? Or is each component balanced on it's own?
Thanks, Tom
Is there anything I need to be mindful of as far as marking things for reinstallation so I don't mess up the balance and cause a vibration? Or is each component balanced on it's own?
Thanks, Tom
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
The flywheel/flexplate is indexed with offset bolt centers and will go on only one way. You can't screw up this part.
Yes, unbolt converter from flexplate and pull the trans back to clear the alignment pins then drop it down. Trans and converter come out and go back in as a unit.
Yes, unbolt converter from flexplate and pull the trans back to clear the alignment pins then drop it down. Trans and converter come out and go back in as a unit.
Thread Starter
Instructor
Joined: Oct 2005
Posts: 113
Likes: 0
From: Melville, Long Island NY
Originally Posted by bobs77vet
don't forget to mark the yoke and driveshaft relationship so the balance is not affected
I assume this is for proper re-assembly (balance) of the driveshaft in relationship to the position of the trans?
Thanks, Tom
Melting Slicks
Joined: Jun 2003
Posts: 2,802
Likes: 241
From: Niles, MI
The TH 350 does not need to come out. Back in the '70s when I was an AT tech at a Chevy dealership I did one of these about once a week.
All you need to do is remove the drive shaft, the crossmember and the bell housing bolts while supporting the trans. Then remove the three bolts that connect the flexplate to the torque convertor and push the torque convertor back into the tranny. You will need to rotate the engine to get at all the bolts. They make special tools that will rotate the engine at the flywheel.
Then separate the tranny from the engine as far as you can. At this point you should be able to access the bolts that secure the flexplate to the crank with a combination wrench. Loosen all the bolts; again you will need to rotate the engine to get at all the bolts. You'll need to smack the wrench with a hammer to get the bolts loose. Once the bolts are out the flexplate should drop right out.
Make sure you replace the starter drive along with the flexplate or you will just wear out your new flexplate.
All you need to do is remove the drive shaft, the crossmember and the bell housing bolts while supporting the trans. Then remove the three bolts that connect the flexplate to the torque convertor and push the torque convertor back into the tranny. You will need to rotate the engine to get at all the bolts. They make special tools that will rotate the engine at the flywheel.
Then separate the tranny from the engine as far as you can. At this point you should be able to access the bolts that secure the flexplate to the crank with a combination wrench. Loosen all the bolts; again you will need to rotate the engine to get at all the bolts. You'll need to smack the wrench with a hammer to get the bolts loose. Once the bolts are out the flexplate should drop right out.
Make sure you replace the starter drive along with the flexplate or you will just wear out your new flexplate.
Last edited by Kid Vette; Dec 12, 2005 at 02:36 PM.
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
TPL79,
I may have a brand new flexplate if you're interested. I'm waiting for a ZZ4 I ordered to arrive which I believe will have one installed. I'll be removing it to install a flywheel. I don't know at this time how many teeth it has, maybe some of the members here can tell you, if not I should have it in a few weeks.
Bill
I may have a brand new flexplate if you're interested. I'm waiting for a ZZ4 I ordered to arrive which I believe will have one installed. I'll be removing it to install a flywheel. I don't know at this time how many teeth it has, maybe some of the members here can tell you, if not I should have it in a few weeks.
Bill
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Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Kid Vette
The TH 350 does not need to come out.
I did a bunch of these when I was with GM, and I never dropped the tranny out of the car. Did just like Kid says: Pull one end of the driveshaft to allow the tranny to slide back, unbolt the converter from the flywheel, unbolt the tranny mount, and unbolt the tranny from the engine. Slide the converter as far back intio the tranny as it will go, support the tranny, and slide it as far back as it will go. You can then pull the flywheel with the tranny in the car. You can have the flywheel out of the car in an hour easy.
