Broke another flexplate, what am I missing?

If it was me, and I was already taking it out and replacing the pump anyways, I'd just rebuild the whole thing with new bushings and clutches and call it a day. Full rebuild kit with BW kolene steels, Raybestos Red clutches, all new bushings, and all the seals and gaskets is only $200 from Jegs: https://www.jegs.com/i/JEGS/555/62142/10002/-1.

Get yourself an ATSG Rebuild manual for another $20 and you're off to the races. https://www.oregonperformancetransmission.com/product/ATSG-350C.html

Blackbeard44 said:

I would fire it up and watch closely for end play in the crankshaft, maybe a thrust bearing has become sloppy.

you sure the motor is definatley a 350, if its a 400 or 327 it will take a different style flexplate.

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Small block 400 is different , but the 327 is the same flex plate as the 350

Everything is internal balance except 400 and 454. (Stock stroke Chevy sb and bbc.)

If you had a 350 fp on a 400 or vice versa you would know real quick.

If your crank pilot and the nose of your converter is not correct that will put your entire trans in a bind.

I’ll say it again first thing to check are those to measurements and verify that the converter turns freely in the back of the pilot.

You say the engine has been rebuilt? Does it have an aftermarket Chinese crankshaft in it? Was the converter made in China?

They are not famous for precision tolerance and machining.

Does your starter grind? Is the starter gear stuck against the flexplate?

This will cause a horrible whine.


Is the engine block cracked where the starter bolts up? Causing the starter to shift and bind.

You should do some more diagnostic checks and inspection before throwing parts a a problem that your not 100% sure of.

Triple check all the small stuff before replacing or buying anything else. You will be glad you did and upset if you don’t.

All good input from everyone just back up take it slow and try to figure out how all these symptoms are related.

Does your fluid color look good? Does the trans slip? Is the flexplate rubbing or grinding against anything? Keep checking until the problem reveals itself then repair that.

BigDaddy72 said:

Everything is internal balance except 400 and 454. (Stock stroke Chevy sb and bbc.)

If you had a 350 fp on a 400 or vice versa you would know real quick.

If your crank pilot and the nose of your converter is not correct that will put your entire trans in a bind.

I’ll say it again first thing to check are those to measurements and verify that the converter turns freely in the back of the pilot.

You say the engine has been rebuilt? Does it have an aftermarket Chinese crankshaft in it? Was the converter made in China?

They are not famous for precision tolerance and machining.

Does your starter grind? Is the starter gear stuck against the flexplate?

This will cause a horrible whine.


Is the engine block cracked where the starter bolts up? Causing the starter to shift and bind.

You should do some more diagnostic checks and inspection before throwing parts a a problem that your not 100% sure of.

Triple check all the small stuff before replacing or buying anything else. You will be glad you did and upset if you don’t.

All good input from everyone just back up take it slow and try to figure out how all these symptoms are related.

Does your fluid color look good? Does the trans slip? Is the flexplate rubbing or grinding against anything? Keep checking until the problem reveals itself then repair that.

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This is really good advice. There's few things more frustrating than spending lots of money to replace a bunch of stuff that doesn't fix the problem you are trying to fix in the first place.

79dentside said:

This truck just has the TH350 in it.

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With the dip stick from a 4l60e?


Nice engine bay btw.

BigDaddy72 said:

Everything is internal balance except 400 and 454. (Stock stroke Chevy sb and bbc.)

If you had a 350 fp on a 400 or vice versa you would know real quick.

If your crank pilot and the nose of your converter is not correct that will put your entire trans in a bind.

I’ll say it again first thing to check are those to measurements and verify that the converter turns freely in the back of the pilot.

You say the engine has been rebuilt? Does it have an aftermarket Chinese crankshaft in it? Was the converter made in China?

They are not famous for precision tolerance and machining.

Does your starter grind? Is the starter gear stuck against the flexplate?

This will cause a horrible whine.


Is the engine block cracked where the starter bolts up? Causing the starter to shift and bind.

You should do some more diagnostic checks and inspection before throwing parts a a problem that your not 100% sure of.

Triple check all the small stuff before replacing or buying anything else. You will be glad you did and upset if you don’t.

All good input from everyone just back up take it slow and try to figure out how all these symptoms are related.

Does your fluid color look good? Does the trans slip? Is the flexplate rubbing or grinding against anything? Keep checking until the problem reveals itself then repair that.

Click to expand...

Good stuff. I really have no issues with this old rig. Starter doesn’t have any issues at all.

As for the crank in the motor, I have no idea. Pretty sure it’s just a new motor. I have no doubts because the inside is stupid clean and there are date marks on the back of the block behind the flexplate when I did it the first time. The truck was pretty much torn apart and then left. Someone tried to fix the truck all up with new parts in 2007, then it was left sitting for years and years. If you notice some orange painted on any of the bolt heads in the engine bay, it’s because they marked all bolts that they took out with orange.. Needless to say every part of this truck has been off of the farm and the body sure does not reflect it lol. Body is junk, the underside is fantastic. There are a lot of mismatching parts in this truck and like gotyourgoat mentioned, it has a 4L dipstick. Same one in my 2001 2500 Suburban. So nothing is true on this thing and I don’t know the individual details of a lot of things.

The trans fluid is cherry red, no slips.

Crack in the block? Cant say I noticed one when I was working by the starter last but I can check.

I can try to unbolt the converter tonight to see if the snout freely spins in that crankshaft bore.

As far as the parts, I used the following pair on my rig. Doubtful that it is the manufactures fault, but I am going to go with higher quality parts this next go around.
https://www.jegs.com/i/JEGS/555/60400K/10002/-1

Thanks for the great advice folks!

If the fluid is good and it shifts fine no slips. Sounds like you have a good transmission.

Let’s us know what you find. You have us all interested now!!

BigDaddy72 said:

If the fluid is good and it shifts fine no slips. Sounds like you have a good transmission.

Let’s us know what you find. You have us all interested now!!

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Going to check the things that you mentioned right now. I’m not sure I want to know how bad the answers are....

thats a sweet looking motor in that beast, I have heard of touque converter getting hot and ballooning out. did it crqck in the same place as the previous flexplate did?

Initial inspection. Torque converter free spins in the crank hub, no block cracks by the starter. Trans pump seal is shot, and have pryed forward on the crank pretty hard, then pryed back with no ‘visible’ endpay. Keep in mind I know we are talking thousands of an inch for spec, but all I am saying is that I see no visible movement after watching it like a hawk. Still need to get a dial indicator, but I am pleased to not see anything obvious... saw a YouTube video where someone had 1/4” of end play and their crank was hitting the block...

I will post a video of another concern.. be back in a bit, had to step away to charge my phone.

79dentside said:

We will see. I’m tempted to put a transmission pump in while I’m there. The transmission has been gone though at some point, I imagine the pump is okay, but you never know.

I’m looking into flexplates and a lower stall converter. All the 2,700 stall made me want to do is keep my foot in it. Driveway has plenty of burnout marks in it, was more playful than I needed it to be.

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I know nothing about flex plates except when the shop that was swapping my BBC 454 in said it had the wrong one on it because it didn't mate with the TC. So $85 got me a new one and no problem with it yet.

Now the BBC is in i can't keep my foot out of either. I too have burnout marks in my driveway. I'm always spinning the tires from a dead stop making the Trans kick down. Slide a couple of corners with a little fan of the throttle.

Its all good bud. It can't be to playful or rowdy. That's the fun!


It does bring me back in time and makes me smile. I love it.

Also me exhaust turns out in front of each rear tire. When it was idling today in the driveway I noticed you probably don't want to pull up next to me at a light with your window down. Lol

82sbshortbed said:

I know nothing about flex plates except when the shop that was swapping my BBC 454 in said it had the wrong one on it because it didn't mate with the TC. So $85 got me a new one and no problem with it yet.

Now the BBC is in i can't keep my foot out of either. I too have burnout marks in my driveway. I'm always spinning the tires from a dead stop making the Trans kick down. Slide a couple of corners with a little fan of the throttle.

Its all good bud. It can't be to playful or rowdy. That's the fun!


It does bring me back in time and makes me smile. I love it.

Also me exhaust turns out in front of each rear tire. When it was idling today in the driveway I noticed you probably don't want to pull up next to me at a light with your window down. Lol

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You sound like you could be my long lost best friend lol. Love the truck brother.

Alright friends... I may have a WHACKED bell housing. I will share ALL of what I found, but I am specifically concerned about my bell housing... check this out fellas... Considering my alignment pin is in the realm of this shotty work, I really hope someone didn’t break the whole corner off and then try to weld it up by eye.. kind of a precise piece there...


Trans pump seal leak (if you look close it features my seeping trans pan gasket too )

Not sure why the starter is chewed up... but there’s that.


Here is a video demo of the torque converter. At the end, I wiggle the converter and it makes noise. Let me know what y’all think....

Somebody sure as hell WAS whackin on it....but wtf for? What's on the other side lol?

....


The wiggle at the video's end looks like pump play? To ME but - I don't know what that is OR looks like even.

It seems to me like whackin on one side of the transmission is VERY suspect AND more information is necessary but it's cold outside...

21°here

Rusty Nail said:

Somebody sure as hell WAS whackin on it....but wtf for? What's on the other side lol?

....


The wiggle at the video's end looks like pump play? To ME but - I don't know what that is OR looks like even.

It seems to me like whackin on one side of the transmission is VERY suspect AND more information is necessary but it's cold outside...

21°here

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Wasn’t me! To be honest, it looks like jb weld and A LOTTT OF IT. I’m wondering if this is an issue. Drivers side is fine, I was about to call it because I was cold and saw the mess on the passenger side... I am more worried about the alignment pin hole that was drilled in... my guess is that it’s oversized and not right.