# Flexplate / flywheel



## gtoearl (Dec 21, 2009)

Well, I had a nightmare last night.... I dreamed I installed the flywheel/ flex plate backwards.... The engine is in and the starter looks a little away from the flywheel teeth....Good thing is I haven't gotten too far with the install to take it back out if necessary. my question is; the flywheel has a concave side and what appears to be a straight or flush side... which side faces the engine? :smash: Thanks guys for your continued input..... forgot in mention...if it helps...I have a t-400 trany...


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## Goat Roper (Oct 28, 2014)

If it is an automatic you have a flex plate.

The shim plate goes on the end of the crank, then the flex plate goes on with the raised part facing the tranny then the bolt plate goes on with the cutout over the tit on the flex plate.
Outer flare on the shim plate faces the engine and the outer flare on the bolt plate goes toward the tranny.
Torque specs are 95 Ft. Lbs. with thread locker.


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## gtoearl (Dec 21, 2009)

Thanks for your response. Your language is a little technical for me, but I think I understand what you're saying. As I said before, The flexplate is already been installed in the motor and is sitting in the car bolted up to the training and bolted up to the torque converter. I have to crawl underneath it in a day or so to see if it meets with your description. But, can you tell me if that concave part of the plate goes towards the engine And the raised part which I described as more straight than concave like the other side, that side would go towards the trany. Also, I had a little difficulty in arranging the orientation of the spacer plate and bowl plate, as the bolt pattern was not evenly distributed around , if that makes sense. I was thinking of hooking up a remote starter button and bumping the engine over to see if the starter is connecting to the flex plate properly. I don't have the dash in yet so there's no ignition switch.


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## Goat Roper (Oct 28, 2014)

The bolt pattern makes it so you can only bolt it up if the three parts are all in line.
Look at the three bolt holes that connect the torque converter to the flex plate, on the flex plate those pads should be raised facing the tranny.
The torque plate has a slot in it that fits over the metal tit so you know it is oriented properly and it only goes on one way.


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## gtoearl (Dec 21, 2009)

Thanks again, if the bolts all went in and bolted up to the flexplate then I guess I got the orientation correct. The question is is it all in the proper order. Won't know that until I get under there and look at it. What do you think about bumping the motor over?


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## Goat Roper (Oct 28, 2014)

You can bump it over with a set of jumper cables, battery + on the large lug on the solenoid ground to the engine and jumper from + battery to the small S terminal on the solenoid.
Make the leads long enough so you are not under the car when you do it.


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## gtoearl (Dec 21, 2009)

Well here it is. The raced part looks to be in the correct position. So I guess it's on correctly. I think what scared me was the warn part of the flex ring seems to be on the wrong side. Maybe sometime during its life it was put on backwards. Does that make sense?


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## Goat Roper (Oct 28, 2014)

It looks right, those flex plates usually have a lot of wear after 50 years and who knows how many starters.
They can also have hairline cracks that may or may not be visible.
The best thing to do when you rebuild one of these older cars is to just replace it, they run around 60 bucks, 80 for a HD.
Also, you have the wrong bolts holding it to the torque converter and you should at least put washers under them to avoid cracks in the plate.
Check out page 279 in the Ames Performance catalog to see the plates and the proper bolts.


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## gtoearl (Dec 21, 2009)

Thanks for all your help! I have to order some parts From Ames. Like you said I'll at least replace the bolts and put washers on them. Thanks 
, I'm sure I'll be posting more issues as I put this thing back together.


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## Goat Roper (Oct 28, 2014)

You're welcome.
You won't need washers they are special shoulder bolt with washer hex heads so just install them.
When I pulled my tranny there was one oddball so I ordered new ones.

That plate has flexed thousands of times and especially if it was bolted like that when you took it apart I would replace it.
If you have ever seen one come apart they can make an expensive mess.


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## tjs72goat (Jul 20, 2017)

I didn't know there was a third component to this as my car was in pieces and didn't have one in the boxes of stuff I got with it. 

"the bolt plate goes on with the cutout over the tit on the flex plate "

I did have the shim plate I put on, then flex plate and then torque converter. Mounted tranny to engine and put in car a few weeks ago. I have the feeling this may have to come apart now if I missed something. It's a 1972 400 with 400 auto. ??


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## PontiacJim (Dec 29, 2012)

tjs72goat said:


> I didn't know there was a third component to this as my car was in pieces and didn't have one in the boxes of stuff I got with it.
> 
> "the bolt plate goes on with the cutout over the tit on the flex plate "
> 
> I did have the shim plate I put on, then flex plate and then torque converter. Mounted tranny to engine and put in car a few weeks ago. I have the feeling this may have to come apart now if I missed something. It's a 1972 400 with 400 auto. ??



Not sure. I have not done many automatics, but only recall bolting them up with the crank bolts having the star washers on them. I found a shim plate on Ebay, and if you look at it, you will see the small "tangs" which is reference to I believe the "tits." I also included the description of what it is and does. Again, I don't recall using one, so you are probably OK.

The most important part is to make sure the torque converter is fully engaged into the front pump on the trans. Once you have your trans in position, push the torque converter back towards the trans body. Then note how far away the ears on the torque converter used to bolt it to the flexplate are from the flexplate holes. You don't want a big gap here. I think is is about 1/8" - 1/4", but don't quote me on it as you can search the web to get the exact gap. If more than that, then you want to add a spacer/flat washer into the gap to get your tolerance correct. I suppose the shim behind the flexplate may be how the factory does it? 

In any case, reason being that if the torque converter is not seated deep enough into the transmission pump, it can cause failure of the pump. I have never had any issues throwing together a stock engine/automatic and never ever checked for the required gap. I just bolted it up and went with it.

So you can check if you choose to, but I'm the lazy type and if its working its working. If it lets go for some reason, then I'll deal with it. I hate overthinking things.

Here is the Ebay description to go with the photo:

"What does the shim plate do? Our understanding is that it is for sound dampening.

Is it necessary to have one? No, the cars don't need one, but they came from the factory with it.

What is the size? 5" across and thin like paper."


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## tjs72goat (Jul 20, 2017)

Thanks. I understand the shim plate. I have that in. But, the previous post here mentioned a bolt plate also, which I never heard of. I also have a spare 400 motor with flex plate and it also has just a shim plate then the flex plate. So, that's all I assumed I needed. Maybe I'm good then. Not sure what this bolt plate is that is referred to above.


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## tjs72goat (Jul 20, 2017)

Goat Roper, what's a bolt plate?


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## Shooter (Nov 7, 2015)

Alright, I just pulled a TH400 out of an old junker. Not sure what's missing. From this thread I'd say I need a:

1) shim plate that goes against the crankshaft
2) flex plate
3) torque converter (bolted to the flex plate)
4) bolt plate
5) bolts to hold it all together (same bolts as if it were a flywheel)

I don't see a bolt plate in my mess. Never heard of one. Where can I buy one? Can't find one on the internet.

Also, don't the shim plates come in different thicknesses? How do you know what thickness you need?

Thanks!


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## PontiacJim (Dec 29, 2012)

Shooter said:


> Alright, I just pulled a TH400 out of an old junker. Not sure what's missing. From this thread I'd say I need a:
> 
> 1) shim plate that goes against the crankshaft
> 2) flex plate
> ...


Here are photo's of the "Bolt Plate" and "Shim Plate." Still can't recall seeing a bolt plate. Have seen the shim plate on some, but not all.






Transmission Parts


Pontiac GTO Trans Am Firebird transsmissions muncie M20 M121 M22 T-350 T400



www.frankspontiacparts.com


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## Shooter (Nov 7, 2015)

PontiacJim,
Man, am I glad you answered this. I have a completely rebuilt 400. Set up with a flywheel. As things change, I am now putting it into a car with an automatic. Was concerned about the balancing of the engine but everything I've read says I can just swap the flywheel for the flex plate. Do flywheels and flex plates use the same bolts to mount to the engine? The flywheel bolts I have are slightly too long. Maybe the "bolt plate" makes up the difference in thickness? Or do I need different bolts?

Shooter


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