Flex plate bolts

[tyler]

So, a looong while back the following exchange was part of a "knocking noise" thread. Jim Hupy told me the bolts could be too long on the flexplate,
and I finally went in there to check today and voila! Threaded to the head, and marks like it bottomed in the converter lug. I am hopeful.

Now, what is the right bolt?

Does the shoulder part really matter, or can I just add a lock washer to this one I have to shorten it up?

___________________________

Tyler, the noise a loose flexplate makes sounds like a broken crankshaft.
Heavy knocking. Diagnose by removing the starter, then the sheet metal
shield. This exposes the attachment bolts. Turn engine by the large nut on
the fan end of the crankshaft, and check the dampener while you are there.
They can mimic this noise. Turn crank until torque converter bolt is
exposed. Remove one and carefully inspect it. It should NOT BE THREADED
upon its full length. The correct bolts will have a large shouldered head,
and the upper portion will have a precision shoulder that is slightly
shorter than the thickness of the flexplate. Check also that the bolts DO
NOT bottom in the converter lug. Look carefully for any signs of bottoming.
Use a strong light source and look in the hole in the torque converter lug.
If it is shiny in the bottom of the hole, the bolts are bottoming before
the flexplate is tightly against the lugs. It will knock like mad if you
find this condition.
Jim Hupy ( aka. the taller brother)
Salem, Oregon

> Asking more on the whole thread, and specifically Dwayne's comment about
> flex plates:
>
> I took my coach to an experienced truck mechanic friend just last week for
> a noise that only happens after driving coach to full operating temp, then
> turning it off, and then restart it from two to maybe twelve minutes later
> (hot restart).
>
> He said he had only ever heard a noise like that one time, a guy had a
> Buick that they eventually found a cracked flexplate.
>
> So, if this is a correct direction for me - does the hot re-start tell me
> anything? And can I see potential cracks or loose bolts from an access panel
> or anything, or is tearing it down the only way to know? I have debated an
> engine oil analysis to learn more engine internal scenario, but then this
> thread came up!
>
--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC

 

[Bruce Hart]

Flex plate bolts can be ASE or Metric depending if torque converter had
been changed.

https://www.ebay.com/itm/Pioneer-859029-SBC-SB-Chevy-Flexplate-Bolts-1pc-Rear-Seal-Crank-Crankshaft/202263338317?fits=Year%3A1976%7CMake%3AChevrolet&epid=112862222&hash=item2f17d59d4d:g:gCcAAOSw2PtarDCG&vxp=mtr

> So, a looong while back the following exchange was part of a "knocking
> noise" thread. Jim Hupy told me the bolts could be too long on the
> flexplate,
> and I finally went in there to check today and voila! Threaded to the
> head, and marks like it bottomed in the converter lug. I am hopeful.
>
> Now, what is the right bolt?
>
> Does the shoulder part really matter, or can I just add a lock washer to
> this one I have to shorten it up?
>
> ___________________________
>
>
> Tyler, the noise a loose flexplate makes sounds like a broken crankshaft.
> Heavy knocking. Diagnose by removing the starter, then the sheet metal
> shield. This exposes the attachment bolts. Turn engine by the large nut on
> the fan end of the crankshaft, and check the dampener while you are there.
> They can mimic this noise. Turn crank until torque converter bolt is
> exposed. Remove one and carefully inspect it. It should NOT BE THREADED
> upon its full length. The correct bolts will have a large shouldered head,
> and the upper portion will have a precision shoulder that is slightly
> shorter than the thickness of the flexplate. Check also that the bolts DO
> NOT bottom in the converter lug. Look carefully for any signs of bottoming.
> Use a strong light source and look in the hole in the torque converter lug.
> If it is shiny in the bottom of the hole, the bolts are bottoming before
> the flexplate is tightly against the lugs. It will knock like mad if you
> find this condition.
> Jim Hupy ( aka. the taller brother)
> Salem, Oregon

>
> > Asking more on the whole thread, and specifically Dwayne's comment about
> > flex plates:
> >
> > I took my coach to an experienced truck mechanic friend just last week
> for
> > a noise that only happens after driving coach to full operating temp,
> then
> > turning it off, and then restart it from two to maybe twelve minutes
> later
> > (hot restart).
> >
> > He said he had only ever heard a noise like that one time, a guy had a
> > Buick that they eventually found a cracked flexplate.
> >
> > So, if this is a correct direction for me - does the hot re-start tell me
> > anything? And can I see potential cracks or loose bolts from an access
> panel
> > or anything, or is tearing it down the only way to know? I have debated
> an
> > engine oil analysis to learn more engine internal scenario, but then this
> > thread came up!
> >
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class

 

[robert mueller]

G'day,

I checked Parts Book 78Z and there are two bolts listed, however, no details are provided other than "procure locally".

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Bruce Hart
Sent: Saturday, March 24, 2018 10:48 AM
To: gmclist
Subject: Re: [GMCnet] Flex plate bolts

Flex plate bolts can be ASE or Metric depending if torque converter had
been changed.

https://www.ebay.com/itm/Pioneer-859029-SBC-SB-Chevy-Flexplate-Bolts-1pc-Rear-Seal-Crank-Crankshaft/202263338317?fits=Year%3A1976%7C
Make%3AChevrolet&epid=112862222&hash=item2f17d59d4d:g:gCcAAOSw2PtarDCG&vxp=mtr

> So, a looong while back the following exchange was part of a "knocking
> noise" thread. Jim Hupy told me the bolts could be too long on the
> flexplate,
> and I finally went in there to check today and voila! Threaded to the
> head, and marks like it bottomed in the converter lug. I am hopeful.
>
> Now, what is the right bolt?
>
> Does the shoulder part really matter, or can I just add a lock washer to
> this one I have to shorten it up?
>
> ___________________________
>
>
> Tyler, the noise a loose flexplate makes sounds like a broken crankshaft.
> Heavy knocking. Diagnose by removing the starter, then the sheet metal
> shield. This exposes the attachment bolts. Turn engine by the large nut on
> the fan end of the crankshaft, and check the dampener while you are there.
> They can mimic this noise. Turn crank until torque converter bolt is
> exposed. Remove one and carefully inspect it. It should NOT BE THREADED
> upon its full length. The correct bolts will have a large shouldered head,
> and the upper portion will have a precision shoulder that is slightly
> shorter than the thickness of the flexplate. Check also that the bolts DO
> NOT bottom in the converter lug. Look carefully for any signs of bottoming.
> Use a strong light source and look in the hole in the torque converter lug.
> If it is shiny in the bottom of the hole, the bolts are bottoming before
> the flexplate is tightly against the lugs. It will knock like mad if you
> find this condition.
> Jim Hupy ( aka. the taller brother)
> Salem, Oregon

>
> > Asking more on the whole thread, and specifically Dwayne's comment about
> > flex plates:
> >
> > I took my coach to an experienced truck mechanic friend just last week
> for
> > a noise that only happens after driving coach to full operating temp,
> then
> > turning it off, and then restart it from two to maybe twelve minutes
> later
> > (hot restart).
> >
> > He said he had only ever heard a noise like that one time, a guy had a
> > Buick that they eventually found a cracked flexplate.
> >
> > So, if this is a correct direction for me - does the hot re-start tell me
> > anything? And can I see potential cracks or loose bolts from an access
> panel
> > or anything, or is tearing it down the only way to know? I have debated
> an
> > engine oil analysis to learn more engine internal scenario, but then this
> > thread came up!
> >
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[tyler]

Bruce, I'm glad you said i might find metric in there, because I sure would not have expected it. The three outside were metric, so the official
packaged bolts available at autozone were for the middle six. I added star lock washers and reinstalled the three bolts that were in there. I did not
see any cracks in the flex plate. And, no difference on noise during the test run. So, the next great idea is welcome.
--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC

 

[Jim Hupy]

What do you mean, the three outside are metric, and middle 6? There are
only three lugs on the CORRECT TORQUE CONVERTER. AND ONLY THREE correct
places for the bolts to go through. If your flex plate or torque converter
are different than I have described, you do not have the correct stuff in
there. There are only two Correct converters for the TM 425. One is metric,
and one is USS. They both only have 3 lugs. If your converter has more than
that, you have the wrong converter.
I suggest that you contact Manny Traveo and verify what you have.
Jim Hupy
Salem, OR
78 GMC Royale 403

> Bruce, I'm glad you said i might find metric in there, because I sure
> would not have expected it. The three outside were metric, so the official
> packaged bolts available at autozone were for the middle six. I added star
> lock washers and reinstalled the three bolts that were in there. I did not
> see any cracks in the flex plate. And, no difference on noise during the
> test run. So, the next great idea is welcome.
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[robert mueller]

Jim,

I think he's talking about the six bolts that hold the flex plate to the crank.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of James Hupy
Sent: Sunday, March 25, 2018 9:27 AM
To: gmclist
Subject: Re: [GMCnet] Flex plate bolts

What do you mean, the three outside are metric, and middle 6? There are
only three lugs on the CORRECT TORQUE CONVERTER. AND ONLY THREE correct
places for the bolts to go through. If your flex plate or torque converter
are different than I have described, you do not have the correct stuff in
there. There are only two Correct converters for the TM 425. One is metric,
and one is USS. They both only have 3 lugs. If your converter has more than
that, you have the wrong converter.
I suggest that you contact Manny Traveo and verify what you have.
Jim Hupy
Salem, OR
78 GMC Royale 403

> Bruce, I'm glad you said i might find metric in there, because I sure
> would not have expected it. The three outside were metric, so the official
> packaged bolts available at autozone were for the middle six. I added star
> lock washers and reinstalled the three bolts that were in there. I did not
> see any cracks in the flex plate. And, no difference on noise during the
> test run. So, the next great idea is welcome.
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[jim kanomata1]

The 3 bolts that go into the converter are metric on some, looking at the
parts book is not valid as the rebuilt units can be metric.

On Sat, Mar 24, 2018 at 3:47 PM, Rob Mueller
wrote:

> Jim,
>
> I think he's talking about the six bolts that hold the flex plate to the
> crank.
>
> Regards,
> Rob M.
> The Pedantic Mechanic
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
> USA '77 Kingsley - TZE 267V100808
>
>
> -----Original Message-----
> From: Gmclist [mailto:gmclist-bounces] On Behalf Of James
> Hupy
> Sent: Sunday, March 25, 2018 9:27 AM
> To: gmclist
> Subject: Re: [GMCnet] Flex plate bolts
>
> What do you mean, the three outside are metric, and middle 6? There are
> only three lugs on the CORRECT TORQUE CONVERTER. AND ONLY THREE correct
> places for the bolts to go through. If your flex plate or torque converter
> are different than I have described, you do not have the correct stuff in
> there. There are only two Correct converters for the TM 425. One is metric,
> and one is USS. They both only have 3 lugs. If your converter has more than
> that, you have the wrong converter.
> I suggest that you contact Manny Traveo and verify what you have.
> Jim Hupy
> Salem, OR
> 78 GMC Royale 403
>

>
> > Bruce, I'm glad you said i might find metric in there, because I sure
> > would not have expected it. The three outside were metric, so the
> official
> > packaged bolts available at autozone were for the middle six. I added
> star
> > lock washers and reinstalled the three bolts that were in there. I did
> not
> > see any cracks in the flex plate. And, no difference on noise during the
> > test run. So, the next great idea is welcome.
> > --
> > 1975 Glenbrook, 1978 Royale rear bath
> > Raleigh, NC
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[Jim Hupy]

There are 6 lug converters. They are not the correct critter. IF they are
mated to a 455 flex plate, bad stuff will happen. I know about the
crankshaft bolts.
Jim Hupy

> The 3 bolts that go into the converter are metric on some, looking at the
> parts book is not valid as the rebuilt units can be metric.
>
> On Sat, Mar 24, 2018 at 3:47 PM, Rob Mueller

>
> > Jim,
> >
> > I think he's talking about the six bolts that hold the flex plate to the
> > crank.
> >
> > Regards,
> > Rob M.
> > The Pedantic Mechanic
> > Sydney, Australia
> > AUS '75 Avion - The Blue Streak TZE365V100428
> > USA '75 Avion - Double Trouble TZE365V100426
> > USA '77 Kingsley - TZE 267V100808
> >
> >
> > -----Original Message-----
> > From: Gmclist [mailto:gmclist-bounces] On Behalf Of
> James
> > Hupy
> > Sent: Sunday, March 25, 2018 9:27 AM
> > To: gmclist
> > Subject: Re: [GMCnet] Flex plate bolts
> >
> > What do you mean, the three outside are metric, and middle 6? There are
> > only three lugs on the CORRECT TORQUE CONVERTER. AND ONLY THREE correct
> > places for the bolts to go through. If your flex plate or torque
> converter
> > are different than I have described, you do not have the correct stuff in
> > there. There are only two Correct converters for the TM 425. One is
> metric,
> > and one is USS. They both only have 3 lugs. If your converter has more
> than
> > that, you have the wrong converter.
> > I suggest that you contact Manny Traveo and verify what you have.
> > Jim Hupy
> > Salem, OR
> > 78 GMC Royale 403
> >

> >
> > > Bruce, I'm glad you said i might find metric in there, because I sure
> > > would not have expected it. The three outside were metric, so the
> > official
> > > packaged bolts available at autozone were for the middle six. I added
> > star
> > > lock washers and reinstalled the three bolts that were in there. I did
> > not
> > > see any cracks in the flex plate. And, no difference on noise during
> the
> > > test run. So, the next great idea is welcome.
> > > --
> > > 1975 Glenbrook, 1978 Royale rear bath
> > > Raleigh, NC
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk
> http://www.appliedgmc.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[kosier]

Jim,

There is at least one correct converter with six lugs. Many years ago I
thought I had
a converter going bad. I had a friend in GM Engineering who had a
connection in
Hydramatic. He offered to have a new converter made to the original specs.
And
also a "special" price. Naturally I went for it. Couple of weeks later he
delivered it.
I paid him and he left. Later when I opened the box, I found it had six
lugs. Damn!
I didn't want to risk screwing it up by hacking three off, so we made three
spacers
slightly thicker than the balance weights on the flex plate and tigged them
on the
flex plate. When I put the Cadillac in, I got a Manny switch pitch and (I
think) I
traded that tranny in to Bounds. Then the 403 with the modified flex plate
went
to Kanomata. I claim no responsibility for whatever happens next.

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
From: "James Hupy"
Sent: Saturday, March 24, 2018 6:26 PM
To:
Subject: Re: [GMCnet] Flex plate bolts

> What do you mean, the three outside are metric, and middle 6? There are
> only three lugs on the CORRECT TORQUE CONVERTER. AND ONLY THREE correct
> places for the bolts to go through. If your flex plate or torque converter
> are different than I have described, you do not have the correct stuff in
> there. There are only two Correct converters for the TM 425. One is
> metric,
> and one is USS. They both only have 3 lugs. If your converter has more
> than
> that, you have the wrong converter.
> I suggest that you contact Manny Traveo and verify what you have.
> Jim Hupy
> Salem, OR
> 78 GMC Royale 403
>

>
>> Bruce, I'm glad you said i might find metric in there, because I sure
>> would not have expected it. The three outside were metric, so the
>> official
>> packaged bolts available at autozone were for the middle six. I added
>> star
>> lock washers and reinstalled the three bolts that were in there. I did
>> not
>> see any cracks in the flex plate. And, no difference on noise during the
>> test run. So, the next great idea is welcome.
>> --
>> 1975 Glenbrook, 1978 Royale rear bath
>> Raleigh, NC
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[tyler]

Not to worry, there were not six bolts to the converter. The bolts sold as flex plate bolts were for the crank. I added star washers to prevent the
bolts I had from bottoming out.

--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC

 

[Jim Hupy]

Gary, always exceptions to NEVER. Converters used in Olds Diesels had 6
lugs and had early lockup as well. Don't know their stall speed, tho. But,
they needed matching flex plates. You install them on a gas flex plate, and
they will wobble, etc.
Jim Hupy

> Not to worry, there were not six bolts to the converter. The bolts sold as
> flex plate bolts were for the crank. I added star washers to prevent the
> bolts I had from bottoming out.
>
>
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>